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Vulnerability Assessment

Weakness
CWE
CWE-787
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, write limits
MITRE ATT&CK

2 techniques across 2 tactics: Execution, Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Impact

CVSS score of 5.4 (MEDIUM). Attack characteristics: network attack vector, low complexity, low privileges required, no user interaction not required.
Exploit ScenarioDerived

A remote attacker could write data beyond allocated buffer boundaries leading to code execution or crashes by sending crafted requests to the affected application.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 1.6% exploitation probability (EPSS)

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AnalysisAI

An issue was discovered in LibVNCServer before 0.9.13. Rated medium severity (CVSS 5.4), this vulnerability is remotely exploitable, low attack complexity. This Out-of-bounds Write vulnerability could allow attackers to write data beyond allocated buffer boundaries leading to code execution or crashes.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Validate write boundaries, use memory-safe languages, enable compiler protections (ASLR, stack canaries).

Affects your stack

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Technical ContextAI · show details

This vulnerability is classified as Out-of-bounds Write (CWE-787), which allows attackers to write data beyond allocated buffer boundaries leading to code execution or crashes. An issue was discovered in LibVNCServer before 0.9.13. libvncserver/rre.c allows out-of-bounds access via encodings. Affected products include: Libvnc Project Libvncserver, Canonical Ubuntu Linux, Debian Debian Linux, Siemens Simatic Itc1500 Firmware, Siemens Simatic Itc1500 Pro Firmware. Version information: before 0.9.13..

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

NVD PRIMARY 5.4 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
Low

DescriptionNVD

An issue was discovered in LibVNCServer before 0.9.13. libvncserver/rre.c allows out-of-bounds access via encodings.

Threat Intelligence Overview

EPSS Score
1.6%
Top 27% exploitable
Data Quality
3 sources
Confidence: Low
NVD CVE.org EPSS GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 1.6%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

29
Low Medium High Critical
KEV: 0
EPSS: +2
CVSS: +27
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Memory Corruption HIGH

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

Affected Products (CPE)NVD

cpe:2.3:a:libvnc_project:libvncserver:*:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:esm:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_itc1500_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_itc1500_pro_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_itc1900_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_itc1900_pro_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_itc2200_firmware:*:*:*:*:*:*:*:*
cpe:2.3:o:siemens:simatic_itc2200_pro_firmware:*:*:*:*:*:*:*:*

More in Libvncserver

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CVE-2018-7225 CRITICAL POC
9.8 Feb 19

An issue was discovered in LibVNCServer through 0.9.11. Rated critical severity (CVSS 9.8), this vulnerability is remote
CVE-2014-6052 HIGH POC
7.5 Dec 15

The HandleRFBServerMessage function in libvncclient/rfbproto.c in LibVNCServer 0.9.9 and earlier does not check certain

CVE-2014-6053 MEDIUM
5.0 Dec 15

The rfbProcessClientNormalMessage function in libvncserver/rfbserver.c in LibVNCServer 0.9.9 and earlier does not proper
CVE-2020-25708 HIGH POC
7.5 Nov 27

A divide by zero issue was found to occur in libvncserver-0.9.12. Rated high severity (CVSS 7.5), this vulnerability is

CVE-2014-6054 MEDIUM
4.3 Oct 06

The rfbProcessClientNormalMessage function in libvncserver/rfbserver.c in LibVNCServer 0.9.9 and earlier allows remote a
CVE-2016-9942 CRITICAL
9.8 Dec 31

Heap-based buffer overflow in ultra.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers to cause a den
CVE-2016-9941 CRITICAL
9.8 Dec 31

Heap-based buffer overflow in rfbproto.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers to cause a

CVE-2018-20020 CRITICAL
9.8 Dec 19

LibVNC before commit 7b1ef0ffc4815cab9a96c7278394152bdc89dc4d contains heap out-of-bound write vulnerability inside stru
CVE-2018-20019 CRITICAL
9.8 Dec 19

LibVNC before commit a83439b9fbe0f03c48eb94ed05729cb016f8b72f contains multiple heap out-of-bound write vulnerabilities

CVE-2018-15127 CRITICAL
9.8 Dec 19

LibVNC before commit 502821828ed00b4a2c4bef90683d0fd88ce495de contains heap out-of-bound write vulnerability in server c
CVE-2018-15126 CRITICAL
9.8 Dec 19

LibVNC before commit 73cb96fec028a576a5a24417b57723b55854ad7b contains heap use-after-free vulnerability in server code

CVE-2014-6051 HIGH
7.5 Sep 30

Integer overflow in the MallocFrameBuffer function in vncviewer.c in LibVNCServer 0.9.9 and earlier allows remote VNC se

Same weakness CWE-787 – Out-of-bounds Write

View all
CVE-2015-3113 CRITICAL POC
9.8
CVE-2011-2462 CRITICAL POC
9.8
CVE-2012-1889 HIGH POC
8.8
CVE-2010-3333 HIGH POC
7.8
CVE-2014-1761 HIGH POC
7.8
CVE-2009-3129 HIGH POC
7.8
CVE-2021-1732 HIGH POC
7.8
CVE-2013-3346 CRITICAL POC
9.8

Same technique Buffer Overflow

View all
CVE-2017-7269 CRITICAL POC
9.8
CVE-2015-5119 CRITICAL POC
9.8
CVE-2020-0796 CRITICAL POC
10.0
CVE-2019-11043 CRITICAL POC
9.8
CVE-2009-0927 HIGH POC
8.8

References

Advisories & patches
PATCH https://cert-portal.siemens.com/productcert/pdf/ssa-390195.pdf PATCH https://github.com/LibVNC/libvncserver/commit/74e8a70f2c9a5248d6718ce443e07c7ed314dfff REF https://github.com/LibVNC/libvncserver/compare/LibVNCServer-0.9.12...LibVNCServer-0.9.13 REF https://lists.debian.org/debian-lts-announce/2020/06/msg00035.html REF https://lists.debian.org/debian-lts-announce/2020/08/msg00045.html REF https://usn.ubuntu.com/4434-1/ REF https://usn.ubuntu.com/4573-1/

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