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Uvnc

39 CVEs vendor

Monthly

CVE-2026-7840 Jul 01, 03:33 CRITICAL Act Now

Remote code execution in the UltraVNC repeater (through version 1.8.2.2) allows an unauthenticated attacker who can reach the built-in HTTP administration port (default TCP 80) to overflow a fixed 1000-byte global buffer and corrupt adjacent .bss globals, leading to arbitrary code execution on the host. The flaw lives in wi_senderr() and wi_replyhdr() in repeater/webgui/webutils.c, where the request URI is copied via unchecked sprintf before any authentication check runs. No public exploit identified at time of analysis, but the CVSS 4.0 base score of 9.3 combined with pre-auth network reachability makes this a high-priority issue.

RCE Buffer Overflow Memory Corruption Ultravnc Uvnc
NVD GitHub VulDB
CVSS 4.0
9.3
EPSS
1.2%
CVE-2026-7839 Jul 01, 03:33 CRITICAL Act Now

Authentication via hardcoded default credentials in UltraVNC repeater through 1.8.2.2 lets any remote attacker who can reach the HTTP administration port (default TCP 80) log in as administrator. On a fresh or unmodified install where settings2.txt is absent, the repeater writes the literal password 'adminadmi2', and the Basic-auth handler enforces no rate-limiting or lockout, so a single well-known credential yields full control over allow/deny rules and session visibility. Rated CVSS 9.1 (CWE-798); no public exploit identified at time of analysis, though the credential itself is disclosed in the advisory.

Authentication Bypass Ultravnc Uvnc
NVD GitHub VulDB
CVSS 3.1
9.1
EPSS
0.3%
CVE-2026-7838 Jul 01, 03:33 HIGH This Week

Remote code execution in the UltraVNC Viewer (all versions through 1.8.2.2) stems from an integer overflow in the RFB failure-response parser: a malicious or man-in-the-middle VNC server can send a reasonLen of 0xFFFFFFFF that wraps to 0 during buffer sizing, then stream 4 GiB into a 256-byte heap allocation. The flaw is reachable pre-authentication through connection-failure and auth-failure messages, so merely connecting a viewer to an attacker-controlled endpoint can corrupt the heap and potentially execute code as the user running the viewer. No public exploit identified at time of analysis, though the researcher confirmed a reliable heap-buffer-overflow write with AddressSanitizer.

RCE Buffer Overflow Integer Overflow Ultravnc Uvnc
NVD GitHub VulDB
CVSS 4.0
8.7
EPSS
1.2%
CVE-2026-7831 Jul 01, 03:33 HIGH This Week

Denial of service in the UltraVNC viewer (vncviewer) through 1.8.2.2 arises from an off-by-one stack buffer overflow in the RFB ServerInit message handler, where a malicious VNC server advertising a desktop name of exactly 2024 bytes forces ReadString to write a NUL terminator at _dn[2024], one byte past a 2024-byte stack buffer. A rogue or compromised server can crash victims who connect to it (reliable process termination on /GS-hardened builds) and potentially corrupt adjacent stack data on canary-less release builds. No public exploit identified at time of analysis, and the flaw is not listed in CISA KEV; exploitation requires the victim to initiate a connection to the attacker-controlled server.

Buffer Overflow Denial Of Service Ultravnc Uvnc
NVD GitHub VulDB
CVSS 3.1
7.6
EPSS
0.4%
CVE-2026-7830 Jul 01, 03:33 HIGH This Week

Credential disclosure in UltraVNC through 1.8.2.2 lets a passive network observer break the MS-Logon II authentication handshake and recover plaintext usernames and passwords. The rfbUltraVNC_MsLogonIIAuth scheme relies on a Diffie-Hellman exchange whose prime fits in an unsigned 64-bit integer and a private exponent derived from time(NULL)-seeded libc rand(), both of which are trivially solvable, so an attacker who sniffs or man-in-the-middles the exchange derives the shared key in seconds to a minute. There is no public exploit identified at time of analysis and no EPSS/KEV signal supplied; CVSS is 7.4 (AC:H reflecting the need to observe the handshake), and MS-Logon III (X25519 + AES-256-GCM) is not affected.

Information Disclosure Microsoft Ultravnc Uvnc
NVD GitHub VulDB
CVSS 3.1
7.4
EPSS
0.2%
CVE-2026-7829 Jul 01, 03:33 HIGH This Week

Remote code execution in the UltraVNC Repeater (through version 1.8.2.2) allows an authenticated administrator to corrupt stack memory via the web GUI allow/deny rule parser, ultimately achieving code execution on the repeater host. The flaw (CWE-787, out-of-bounds write) is reachable only after admin login, but that barrier is significantly weakened when chained with CVE-2026-7839 (default password), which can hand an attacker the required credentials. There is no public exploit identified at time of analysis and no EPSS/KEV data supplied, so this is currently a credentialed, chainable RCE rather than a confirmed mass-exploited threat.

RCE Buffer Overflow Memory Corruption Ultravnc Uvnc
NVD GitHub VulDB
CVSS 3.1
7.2
EPSS
0.5%
CVE-2026-7828 Jul 01, 03:33 MEDIUM This Month

Heap buffer overflow in UltraVNC Repeater through 1.8.2.2 stems from an integer overflow in the HTTP request logging function win_log(), where a malloc size calculation wraps around on 32-bit builds when processing oversized URIs, producing an undersized heap allocation followed by an unchecked strcpy. Remote unauthenticated attackers can trigger this path by sending a maximally-sized URI to the repeater HTTP port, with practical impact bounded by the 153,600-byte HTTP receive buffer and currently assessed at availability disruption rather than reliable code execution. No public exploit code has been identified at time of analysis, and this CVE is not listed in CISA KEV.

Buffer Overflow Integer Overflow Ultravnc Uvnc
NVD GitHub
CVSS 3.1
5.3
EPSS
0.8%
CVE-2026-44040 Jul 01, 03:33 MEDIUM This Month

UltraVNC through 1.8.2.2 exposes a cryptographically weak VNC authentication challenge generator that an attacker can predict by observing network traffic and enumerating a roughly 31-bit seed space derived from wall-clock time and process ID. Successful seed reconstruction allows the attacker to forge or brute-force valid VNC authentication responses, effectively bypassing the RFB challenge-response mechanism and gaining unauthorized remote desktop access. No public exploit has been identified at time of analysis, and the vulnerability is not currently listed in the CISA KEV catalog; however, the mathematical basis for exploitation is straightforward given the small seed space.

Information Disclosure Microsoft Ultravnc Uvnc
NVD GitHub VulDB
CVSS 3.1
6.5
EPSS
0.2%
CVE-2026-44041 Jul 01, 03:33 MEDIUM This Month

Out-of-bounds read in UltraVNC through version 1.8.2.2 allows network-authenticated attackers to potentially crash the VNC server process or leak adjacent memory content via the vncWc2Mb() wide-string conversion helper in rfb/dh.cpp at line 204. The flaw is triggered when wcslen() is called on a caller-supplied WCHAR pointer without a preceding bounds check, enabling memory over-reads if the buffer lacks proper NUL termination. No public exploit code or active exploitation has been identified at time of analysis; the vendor's CVSS 4.3 (Medium) rating reflects the constrained and largely denial-of-service-oriented impact.

Buffer Overflow Denial Of Service Information Disclosure Ultravnc Uvnc
NVD GitHub VulDB
CVSS 3.1
6.5
EPSS
0.3%
CVE-2026-44042 Jul 01, 03:33 LOW Monitor

UltraVNC Repeater through 1.8.2.2 harbors a latent off-by-one stack buffer boundary condition in its HTTP Basic authentication Base64 decoder, where a strict greater-than comparison at `repeater/webgui/webutils.c:817` fails to block an input whose length exactly equals the 1024-byte output buffer. Under current code, the outer HTTP request parser incidentally caps Authorization header length before the defect can produce an out-of-bounds write, making this vulnerability practically unexploitable in its present form - but the flaw is real and would become a one-byte stack write if upstream buffering constraints change. No public exploit code exists and the vulnerability is not listed in CISA KEV; this is a latent memory-safety defect requiring patch application as hygiene rather than urgent incident response.

Buffer Overflow Ultravnc Uvnc
NVD GitHub VulDB
CVSS 3.1
3.7
EPSS
0.3%
CVE-2019-25601 Mar 22, 13:38 MEDIUM POC This Month

UltraVNC Launcher 1.2.2.4 contains a buffer overflow vulnerability in the Path vncviewer.exe property field that allows local attackers to crash the application by supplying an excessively long. Rated medium severity (CVSS 6.9), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

Buffer Overflow Denial Of Service Memory Corruption Ultravnc Launcher Uvnc
NVD Exploit-DB
CVSS 4.0
6.9
EPSS
0.0%
CVE-2019-25600 Mar 22, 13:38 HIGH POC This Week

UltraVNC Viewer 1.2.2.4 contains a denial of service vulnerability that allows attackers to crash the application by supplying an oversized string to the VNC Server input field.

Buffer Overflow Denial Of Service Memory Corruption Ultravnc Viewer Uvnc
NVD Exploit-DB
CVSS 4.0
7.1
EPSS
0.0%
CVE-2019-25564 Mar 21, 12:47 MEDIUM POC This Month

PCHelpWareV2 1.0.0.5 contains a denial of service vulnerability that allows local attackers to crash the application by supplying an excessively long string in the Group field. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

Buffer Overflow Denial Of Service Memory Corruption Pchelpwarev2 Uvnc
NVD Exploit-DB VulDB
CVSS 3.1
5.5
EPSS
0.0%
CVE-2019-25563 Mar 21, 12:47 MEDIUM POC This Month

PCHelpWareV2 1.0.0.5 contains a denial of service vulnerability that allows local attackers to crash the application by supplying a malformed image file. Rated medium severity (CVSS 6.2), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

Denial Of Service Pchelpwarev2 Uvnc
NVD Exploit-DB VulDB
CVSS 3.1
6.2
EPSS
0.0%
CVE-2026-3787 Mar 08, 23:15 MEDIUM This Month

UltraVNC 1.6.4.0 on Windows contains an uncontrolled search path vulnerability in cryptbase.dll that allows local authenticated attackers with low privileges to achieve arbitrary code execution through DLL hijacking. Successful exploitation requires local access and considerable technical complexity, though the vendor has not provided a patch despite early disclosure notification. This vulnerability carries a high impact rating with potential for complete system compromise (confidentiality, integrity, and availability).

Information Disclosure Microsoft Ultravnc Uvnc
NVD VulDB
CVSS 4.0
6.4
EPSS
0.0%
CVE-2020-37133 Feb 05, 17:16 HIGH POC This Week

UltraVNC Launcher 1.2.4.0 contains a denial of service vulnerability in the Repeater Host configuration field that allows attackers to crash the application. Attackers can paste an overly long string of 300 characters into the Repeater Host property to trigger an application crash. [CVSS 7.5 HIGH]

Denial Of Service Ultravnc Uvnc
NVD Exploit-DB
CVSS 3.1
7.5
EPSS
0.0%
CVE-2020-37132 Feb 05, 17:16 MEDIUM POC This Month

UltraVNC Launcher 1.2.4.0 contains a denial of service vulnerability in its password configuration properties that allows local attackers to crash the application. [CVSS 6.2 MEDIUM]

Denial Of Service Ultravnc Uvnc
NVD Exploit-DB
CVSS 3.1
6.2
EPSS
0.0%
CVE-2022-24750 Mar 10, 21:15 HIGH PATCH This Week

UltraVNC is a free and open source remote pc access software. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. This Improper Privilege Management vulnerability could allow attackers to escalate privileges to gain unauthorized elevated access.

Privilege Escalation Ultravnc Uvnc
NVD GitHub
CVSS 3.1
7.8
EPSS
0.3%
CVE-2019-8280 Mar 08, 23:29 CRITICAL Act Now

UltraVNC revision 1203 has out-of-bounds access vulnerability in VNC client inside RAW decoder, which can potentially result code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Ultravnc Uvnc
NVD
CVSS 3.0
9.8
EPSS
4.2%
CVE-2019-8277 Mar 08, 23:29 HIGH This Week

UltraVNC revision 1211 contains multiple memory leaks (CWE-665) in VNC server code, which allows an attacker to read stack memory and can be abused for information disclosure. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Information Disclosure Siemens Ultravnc Sinumerik Access Mymachine P2P Sinumerik Pcu Base Win10 Software Ipc +2
NVD
CVSS 3.1
7.5
EPSS
3.0%
CVE-2019-8276 Mar 08, 23:29 HIGH This Week

UltraVNC revision 1211 has a stack buffer overflow vulnerability in VNC server code inside file transfer request handler, which can result in Denial of Service (DoS). Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Denial Of Service Stack Overflow Siemens Ultravnc +4
NVD
CVSS 3.1
7.5
EPSS
5.7%
CVE-2019-8275 Mar 08, 23:29 CRITICAL Act Now

UltraVNC revision 1211 has multiple improper null termination vulnerabilities in VNC server code, which result in out-of-bound data being accessed by remote users. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Information Disclosure Siemens Ultravnc Sinumerik Access Mymachine P2P Sinumerik Pcu Base Win10 Software Ipc +2
NVD
CVSS 3.1
9.8
EPSS
4.0%
CVE-2019-8274 Mar 08, 23:29 CRITICAL Act Now

UltraVNC revision 1211 has a heap buffer overflow vulnerability in VNC server code inside file transfer offer handler, which can potentially in result code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Buffer Overflow Heap Overflow Siemens Ultravnc +4
NVD
CVSS 3.1
9.8
EPSS
8.3%
CVE-2019-8273 Mar 08, 23:29 CRITICAL Act Now

UltraVNC revision 1211 has a heap buffer overflow vulnerability in VNC server code inside file transfer request handler, which can potentially result in code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Buffer Overflow Heap Overflow Siemens Ultravnc +4
NVD
CVSS 3.1
9.8
EPSS
8.3%
CVE-2019-8272 Mar 08, 23:29 CRITICAL Act Now

UltraVNC revision 1211 has multiple off-by-one vulnerabilities in VNC server code, which can potentially result in code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Siemens Ultravnc Sinumerik Access Mymachine P2P Sinumerik Pcu Base Win10 Software Ipc +2
NVD
CVSS 3.1
9.8
EPSS
3.9%
CVE-2019-8271 Mar 08, 23:29 CRITICAL Act Now

UltraVNC revision 1211 has a heap buffer overflow vulnerability in VNC server code inside file transfer handler, which can potentially result code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Buffer Overflow Heap Overflow Siemens Ultravnc +4
NVD
CVSS 3.1
9.8
EPSS
8.3%
CVE-2019-8270 Mar 08, 23:29 HIGH This Week

UltraVNC revision 1210 has out-of-bounds read vulnerability in VNC client code inside Ultra decoder, which results in a denial of service (DoS) condition. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Denial Of Service Information Disclosure Ultravnc Uvnc
NVD
CVSS 3.0
7.5
EPSS
1.9%
CVE-2019-8269 Mar 08, 23:29 HIGH This Week

UltraVNC revision 1206 has stack-based Buffer overflow vulnerability in VNC client code inside FileTransfer module, which leads to a denial of service (DoS) condition. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Denial Of Service Stack Overflow Siemens Ultravnc +4
NVD
CVSS 3.1
7.5
EPSS
5.7%
CVE-2019-8268 Mar 08, 23:29 CRITICAL Act Now

UltraVNC revision 1206 has multiple off-by-one vulnerabilities in VNC client code connected with improper usage of ClientConnection::ReadString function, which can potentially result code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Siemens Ultravnc Sinumerik Access Mymachine P2P Sinumerik Pcu Base Win10 Software Ipc +2
NVD
CVSS 3.1
9.8
EPSS
3.9%
CVE-2019-8267 Mar 08, 23:29 HIGH This Week

UltraVNC revision 1207 has out-of-bounds read vulnerability in VNC client code inside TextChat module, which results in a denial of service (DoS) condition. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Denial Of Service Information Disclosure Ultravnc Uvnc
NVD
CVSS 3.0
7.5
EPSS
1.9%
CVE-2019-8266 Mar 08, 23:29 CRITICAL Act Now

UltraVNC revision 1207 has multiple out-of-bounds access vulnerabilities connected with improper usage of ClientConnection::Copybuffer function in VNC client code, which can potentially result in. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Ultravnc Uvnc
NVD
CVSS 3.0
9.8
EPSS
2.8%
CVE-2019-8265 Mar 08, 23:29 CRITICAL Act Now

UltraVNC revision 1207 has multiple out-of-bounds access vulnerabilities connected with improper usage of SETPIXELS macro in VNC client code, which can potentially result in code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Ultravnc Uvnc
NVD
CVSS 3.0
9.8
EPSS
3.1%
CVE-2019-8264 Mar 08, 23:29 CRITICAL Act Now

UltraVNC revision 1203 has out-of-bounds access vulnerability in VNC client inside Ultra2 decoder, which can potentially result in code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Ultravnc Uvnc
NVD
CVSS 3.0
9.8
EPSS
3.1%
CVE-2019-8263 Mar 05, 15:29 MEDIUM This Month

UltraVNC revision 1205 has stack-based buffer overflow vulnerability in VNC client code inside ShowConnInfo routine, which leads to a denial of service (DoS) condition. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Denial Of Service Stack Overflow Siemens Ultravnc +4
NVD
CVSS 3.1
6.5
EPSS
2.5%
CVE-2019-8262 Mar 05, 15:29 CRITICAL Act Now

UltraVNC revision 1203 has multiple heap buffer overflow vulnerabilities in VNC client code inside Ultra decoder, which results in code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Buffer Overflow Heap Overflow Siemens Ultravnc +4
NVD
CVSS 3.1
9.8
EPSS
4.8%
CVE-2019-8261 Mar 05, 15:29 CRITICAL Act Now

UltraVNC revision 1199 has a out-of-bounds read vulnerability in VNC code inside client CoRRE decoder, caused by multiplication overflow. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Information Disclosure Ultravnc Uvnc
NVD
CVSS 3.0
9.8
EPSS
2.2%
CVE-2019-8260 Mar 05, 15:29 CRITICAL Act Now

UltraVNC revision 1199 has a out-of-bounds read vulnerability in VNC client RRE decoder code, caused by multiplication overflow. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Information Disclosure Ultravnc Uvnc
NVD
CVSS 3.0
9.8
EPSS
2.3%
CVE-2019-8259 Mar 05, 15:29 HIGH This Week

UltraVNC revision 1198 contains multiple memory leaks (CWE-655) in VNC client code, which allow an attacker to read stack memory and can be abused for information disclosure. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Information Disclosure Siemens Ultravnc Sinumerik Access Mymachine P2P Sinumerik Pcu Base Win10 Software Ipc +2
NVD
CVSS 3.1
7.5
EPSS
3.0%
CVE-2019-8258 Mar 05, 15:29 CRITICAL Act Now

UltraVNC revision 1198 has a heap buffer overflow vulnerability in VNC client code which results code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Buffer Overflow Heap Overflow Siemens Ultravnc +4
NVD
CVSS 3.1
9.8
EPSS
4.4%
EPSS 1% CVSS 9.3
CRITICAL Act Now

Remote code execution in the UltraVNC repeater (through version 1.8.2.2) allows an unauthenticated attacker who can reach the built-in HTTP administration port (default TCP 80) to overflow a fixed 1000-byte global buffer and corrupt adjacent .bss globals, leading to arbitrary code execution on the host. The flaw lives in wi_senderr() and wi_replyhdr() in repeater/webgui/webutils.c, where the request URI is copied via unchecked sprintf before any authentication check runs. No public exploit identified at time of analysis, but the CVSS 4.0 base score of 9.3 combined with pre-auth network reachability makes this a high-priority issue.

RCE Buffer Overflow Memory Corruption +2
NVD GitHub VulDB
EPSS 0% CVSS 9.1
CRITICAL Act Now

Authentication via hardcoded default credentials in UltraVNC repeater through 1.8.2.2 lets any remote attacker who can reach the HTTP administration port (default TCP 80) log in as administrator. On a fresh or unmodified install where settings2.txt is absent, the repeater writes the literal password 'adminadmi2', and the Basic-auth handler enforces no rate-limiting or lockout, so a single well-known credential yields full control over allow/deny rules and session visibility. Rated CVSS 9.1 (CWE-798); no public exploit identified at time of analysis, though the credential itself is disclosed in the advisory.

Authentication Bypass Ultravnc Uvnc
NVD GitHub VulDB
EPSS 1% CVSS 8.7
HIGH This Week

Remote code execution in the UltraVNC Viewer (all versions through 1.8.2.2) stems from an integer overflow in the RFB failure-response parser: a malicious or man-in-the-middle VNC server can send a reasonLen of 0xFFFFFFFF that wraps to 0 during buffer sizing, then stream 4 GiB into a 256-byte heap allocation. The flaw is reachable pre-authentication through connection-failure and auth-failure messages, so merely connecting a viewer to an attacker-controlled endpoint can corrupt the heap and potentially execute code as the user running the viewer. No public exploit identified at time of analysis, though the researcher confirmed a reliable heap-buffer-overflow write with AddressSanitizer.

RCE Buffer Overflow Integer Overflow +2
NVD GitHub VulDB
EPSS 0% CVSS 7.6
HIGH This Week

Denial of service in the UltraVNC viewer (vncviewer) through 1.8.2.2 arises from an off-by-one stack buffer overflow in the RFB ServerInit message handler, where a malicious VNC server advertising a desktop name of exactly 2024 bytes forces ReadString to write a NUL terminator at _dn[2024], one byte past a 2024-byte stack buffer. A rogue or compromised server can crash victims who connect to it (reliable process termination on /GS-hardened builds) and potentially corrupt adjacent stack data on canary-less release builds. No public exploit identified at time of analysis, and the flaw is not listed in CISA KEV; exploitation requires the victim to initiate a connection to the attacker-controlled server.

Buffer Overflow Denial Of Service Ultravnc +1
NVD GitHub VulDB
EPSS 0% CVSS 7.4
HIGH This Week

Credential disclosure in UltraVNC through 1.8.2.2 lets a passive network observer break the MS-Logon II authentication handshake and recover plaintext usernames and passwords. The rfbUltraVNC_MsLogonIIAuth scheme relies on a Diffie-Hellman exchange whose prime fits in an unsigned 64-bit integer and a private exponent derived from time(NULL)-seeded libc rand(), both of which are trivially solvable, so an attacker who sniffs or man-in-the-middles the exchange derives the shared key in seconds to a minute. There is no public exploit identified at time of analysis and no EPSS/KEV signal supplied; CVSS is 7.4 (AC:H reflecting the need to observe the handshake), and MS-Logon III (X25519 + AES-256-GCM) is not affected.

Information Disclosure Microsoft Ultravnc +1
NVD GitHub VulDB
EPSS 1% CVSS 7.2
HIGH This Week

Remote code execution in the UltraVNC Repeater (through version 1.8.2.2) allows an authenticated administrator to corrupt stack memory via the web GUI allow/deny rule parser, ultimately achieving code execution on the repeater host. The flaw (CWE-787, out-of-bounds write) is reachable only after admin login, but that barrier is significantly weakened when chained with CVE-2026-7839 (default password), which can hand an attacker the required credentials. There is no public exploit identified at time of analysis and no EPSS/KEV data supplied, so this is currently a credentialed, chainable RCE rather than a confirmed mass-exploited threat.

RCE Buffer Overflow Memory Corruption +2
NVD GitHub VulDB
EPSS 1% CVSS 5.3
MEDIUM This Month

Heap buffer overflow in UltraVNC Repeater through 1.8.2.2 stems from an integer overflow in the HTTP request logging function win_log(), where a malloc size calculation wraps around on 32-bit builds when processing oversized URIs, producing an undersized heap allocation followed by an unchecked strcpy. Remote unauthenticated attackers can trigger this path by sending a maximally-sized URI to the repeater HTTP port, with practical impact bounded by the 153,600-byte HTTP receive buffer and currently assessed at availability disruption rather than reliable code execution. No public exploit code has been identified at time of analysis, and this CVE is not listed in CISA KEV.

Buffer Overflow Integer Overflow Ultravnc +1
NVD GitHub
EPSS 0% CVSS 6.5
MEDIUM This Month

UltraVNC through 1.8.2.2 exposes a cryptographically weak VNC authentication challenge generator that an attacker can predict by observing network traffic and enumerating a roughly 31-bit seed space derived from wall-clock time and process ID. Successful seed reconstruction allows the attacker to forge or brute-force valid VNC authentication responses, effectively bypassing the RFB challenge-response mechanism and gaining unauthorized remote desktop access. No public exploit has been identified at time of analysis, and the vulnerability is not currently listed in the CISA KEV catalog; however, the mathematical basis for exploitation is straightforward given the small seed space.

Information Disclosure Microsoft Ultravnc +1
NVD GitHub VulDB
EPSS 0% CVSS 6.5
MEDIUM This Month

Out-of-bounds read in UltraVNC through version 1.8.2.2 allows network-authenticated attackers to potentially crash the VNC server process or leak adjacent memory content via the vncWc2Mb() wide-string conversion helper in rfb/dh.cpp at line 204. The flaw is triggered when wcslen() is called on a caller-supplied WCHAR pointer without a preceding bounds check, enabling memory over-reads if the buffer lacks proper NUL termination. No public exploit code or active exploitation has been identified at time of analysis; the vendor's CVSS 4.3 (Medium) rating reflects the constrained and largely denial-of-service-oriented impact.

Buffer Overflow Denial Of Service Information Disclosure +2
NVD GitHub VulDB
EPSS 0% CVSS 3.7
LOW Monitor

UltraVNC Repeater through 1.8.2.2 harbors a latent off-by-one stack buffer boundary condition in its HTTP Basic authentication Base64 decoder, where a strict greater-than comparison at `repeater/webgui/webutils.c:817` fails to block an input whose length exactly equals the 1024-byte output buffer. Under current code, the outer HTTP request parser incidentally caps Authorization header length before the defect can produce an out-of-bounds write, making this vulnerability practically unexploitable in its present form - but the flaw is real and would become a one-byte stack write if upstream buffering constraints change. No public exploit code exists and the vulnerability is not listed in CISA KEV; this is a latent memory-safety defect requiring patch application as hygiene rather than urgent incident response.

Buffer Overflow Ultravnc Uvnc
NVD GitHub VulDB
EPSS 0% CVSS 6.9
MEDIUM POC This Month

UltraVNC Launcher 1.2.2.4 contains a buffer overflow vulnerability in the Path vncviewer.exe property field that allows local attackers to crash the application by supplying an excessively long. Rated medium severity (CVSS 6.9), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

Buffer Overflow Denial Of Service Memory Corruption +2
NVD Exploit-DB
EPSS 0% CVSS 7.1
HIGH POC This Week

UltraVNC Viewer 1.2.2.4 contains a denial of service vulnerability that allows attackers to crash the application by supplying an oversized string to the VNC Server input field.

Buffer Overflow Denial Of Service Memory Corruption +2
NVD Exploit-DB
EPSS 0% CVSS 5.5
MEDIUM POC This Month

PCHelpWareV2 1.0.0.5 contains a denial of service vulnerability that allows local attackers to crash the application by supplying an excessively long string in the Group field. Rated medium severity (CVSS 5.5), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

Buffer Overflow Denial Of Service Memory Corruption +2
NVD Exploit-DB VulDB
EPSS 0% CVSS 6.2
MEDIUM POC This Month

PCHelpWareV2 1.0.0.5 contains a denial of service vulnerability that allows local attackers to crash the application by supplying a malformed image file. Rated medium severity (CVSS 6.2), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

Denial Of Service Pchelpwarev2 Uvnc
NVD Exploit-DB VulDB
EPSS 0% CVSS 6.4
MEDIUM This Month

UltraVNC 1.6.4.0 on Windows contains an uncontrolled search path vulnerability in cryptbase.dll that allows local authenticated attackers with low privileges to achieve arbitrary code execution through DLL hijacking. Successful exploitation requires local access and considerable technical complexity, though the vendor has not provided a patch despite early disclosure notification. This vulnerability carries a high impact rating with potential for complete system compromise (confidentiality, integrity, and availability).

Information Disclosure Microsoft Ultravnc +1
NVD VulDB
EPSS 0% CVSS 7.5
HIGH POC This Week

UltraVNC Launcher 1.2.4.0 contains a denial of service vulnerability in the Repeater Host configuration field that allows attackers to crash the application. Attackers can paste an overly long string of 300 characters into the Repeater Host property to trigger an application crash. [CVSS 7.5 HIGH]

Denial Of Service Ultravnc Uvnc
NVD Exploit-DB
EPSS 0% CVSS 6.2
MEDIUM POC This Month

UltraVNC Launcher 1.2.4.0 contains a denial of service vulnerability in its password configuration properties that allows local attackers to crash the application. [CVSS 6.2 MEDIUM]

Denial Of Service Ultravnc Uvnc
NVD Exploit-DB
EPSS 0% CVSS 7.8
HIGH PATCH This Week

UltraVNC is a free and open source remote pc access software. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. This Improper Privilege Management vulnerability could allow attackers to escalate privileges to gain unauthorized elevated access.

Privilege Escalation Ultravnc Uvnc
NVD GitHub
EPSS 4% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1203 has out-of-bounds access vulnerability in VNC client inside RAW decoder, which can potentially result code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Ultravnc Uvnc
NVD
EPSS 3% CVSS 7.5
HIGH This Week

UltraVNC revision 1211 contains multiple memory leaks (CWE-665) in VNC server code, which allows an attacker to read stack memory and can be abused for information disclosure. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Information Disclosure Siemens Ultravnc +4
NVD
EPSS 6% CVSS 7.5
HIGH This Week

UltraVNC revision 1211 has a stack buffer overflow vulnerability in VNC server code inside file transfer request handler, which can result in Denial of Service (DoS). Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Denial Of Service Stack Overflow +6
NVD
EPSS 4% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1211 has multiple improper null termination vulnerabilities in VNC server code, which result in out-of-bound data being accessed by remote users. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Information Disclosure Siemens Ultravnc +4
NVD
EPSS 8% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1211 has a heap buffer overflow vulnerability in VNC server code inside file transfer offer handler, which can potentially in result code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Buffer Overflow Heap Overflow +6
NVD
EPSS 8% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1211 has a heap buffer overflow vulnerability in VNC server code inside file transfer request handler, which can potentially result in code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Buffer Overflow Heap Overflow +6
NVD
EPSS 4% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1211 has multiple off-by-one vulnerabilities in VNC server code, which can potentially result in code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Siemens Ultravnc +4
NVD
EPSS 8% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1211 has a heap buffer overflow vulnerability in VNC server code inside file transfer handler, which can potentially result code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Buffer Overflow Heap Overflow +6
NVD
EPSS 2% CVSS 7.5
HIGH This Week

UltraVNC revision 1210 has out-of-bounds read vulnerability in VNC client code inside Ultra decoder, which results in a denial of service (DoS) condition. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Denial Of Service Information Disclosure +2
NVD
EPSS 6% CVSS 7.5
HIGH This Week

UltraVNC revision 1206 has stack-based Buffer overflow vulnerability in VNC client code inside FileTransfer module, which leads to a denial of service (DoS) condition. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Denial Of Service Stack Overflow +6
NVD
EPSS 4% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1206 has multiple off-by-one vulnerabilities in VNC client code connected with improper usage of ClientConnection::ReadString function, which can potentially result code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Siemens Ultravnc +4
NVD
EPSS 2% CVSS 7.5
HIGH This Week

UltraVNC revision 1207 has out-of-bounds read vulnerability in VNC client code inside TextChat module, which results in a denial of service (DoS) condition. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Denial Of Service Information Disclosure +2
NVD
EPSS 3% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1207 has multiple out-of-bounds access vulnerabilities connected with improper usage of ClientConnection::Copybuffer function in VNC client code, which can potentially result in. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Ultravnc Uvnc
NVD
EPSS 3% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1207 has multiple out-of-bounds access vulnerabilities connected with improper usage of SETPIXELS macro in VNC client code, which can potentially result in code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Ultravnc Uvnc
NVD
EPSS 3% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1203 has out-of-bounds access vulnerability in VNC client inside Ultra2 decoder, which can potentially result in code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Ultravnc Uvnc
NVD
EPSS 2% CVSS 6.5
MEDIUM This Month

UltraVNC revision 1205 has stack-based buffer overflow vulnerability in VNC client code inside ShowConnInfo routine, which leads to a denial of service (DoS) condition. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Denial Of Service Stack Overflow +6
NVD
EPSS 5% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1203 has multiple heap buffer overflow vulnerabilities in VNC client code inside Ultra decoder, which results in code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Buffer Overflow Heap Overflow +6
NVD
EPSS 2% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1199 has a out-of-bounds read vulnerability in VNC code inside client CoRRE decoder, caused by multiplication overflow. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Information Disclosure Ultravnc +1
NVD
EPSS 2% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1199 has a out-of-bounds read vulnerability in VNC client RRE decoder code, caused by multiplication overflow. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Buffer Overflow Information Disclosure Ultravnc +1
NVD
EPSS 3% CVSS 7.5
HIGH This Week

UltraVNC revision 1198 contains multiple memory leaks (CWE-655) in VNC client code, which allow an attacker to read stack memory and can be abused for information disclosure. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

Information Disclosure Siemens Ultravnc +4
NVD
EPSS 4% CVSS 9.8
CRITICAL Act Now

UltraVNC revision 1198 has a heap buffer overflow vulnerability in VNC client code which results code execution. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

RCE Buffer Overflow Heap Overflow +6
NVD

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