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Vulnerability Assessment

Weakness
CWE
CWE-476
OWASP Top 10:2025
A10:2025 - Mishandling of Exceptional Conditions
ASVS 5.0
V16 - Security Logging and Error Handling Null pointer safety, defensive checks
MITRE ATT&CK

1 technique across 1 tactic: Impact

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 7.5 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived

A remote attacker could crash the application by dereferencing a null pointer by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 3.4% exploitation probability (EPSS)

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AnalysisAI

An issue was discovered in LibVNCServer before 0.9.13. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This NULL Pointer Dereference vulnerability could allow attackers to crash the application by dereferencing a null pointer.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Check pointers before dereferencing. Use static analysis tools to detect null pointer paths.

Affects your stack

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Technical ContextAI · show details

This vulnerability is classified as NULL Pointer Dereference (CWE-476), which allows attackers to crash the application by dereferencing a null pointer. An issue was discovered in LibVNCServer before 0.9.13. libvncserver/rfbregion.c has a NULL pointer dereference. 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 7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

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

DescriptionNVD

An issue was discovered in LibVNCServer before 0.9.13. libvncserver/rfbregion.c has a NULL pointer dereference.

Threat Intelligence Overview

EPSS Score
3.4%
Top 13% 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 HIGH
CISA KEV No
Public POC No
EPSS 3.4%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
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
Yes
Human Impact· derived
Medium

Priority Score

41
Low Medium High Critical
KEV: 0
EPSS: +3
CVSS: +38
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Null Pointer Dereference MEDIUM

A null pointer dereference occurs when a program attempts to access memory through a pointer that has been set to NULL (address 0x0).

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

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:*:*:*:*:*:*:*:*
cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*

More in Libvncserver

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

CVE-2014-6053 MEDIUM
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The rfbProcessClientNormalMessage function in libvncserver/rfbserver.c in LibVNCServer 0.9.9 and earlier does not proper
CVE-2020-25708 HIGH POC
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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
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The rfbProcessClientNormalMessage function in libvncserver/rfbserver.c in LibVNCServer 0.9.9 and earlier allows remote a
CVE-2016-9942 CRITICAL
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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
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Heap-based buffer overflow in rfbproto.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers to cause a

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CVE-2018-20019 CRITICAL
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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
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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-476 – NULL Pointer Dereference

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CVE-2016-0742 HIGH
7.5
CVE-2014-3470 MEDIUM
4.3
CVE-2020-1967 HIGH POC
7.5
CVE-2017-3730 HIGH POC
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CVE-2017-3169 CRITICAL POC
9.8
CVE-2016-4957 HIGH
7.5
CVE-2021-3449 MEDIUM
5.9
CVE-2015-3194 HIGH
7.5

Same technique Denial Of Service

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CVE-2015-5119 CRITICAL POC
9.8
CVE-2011-2462 CRITICAL POC
9.8
CVE-2011-0611 HIGH POC
8.8
CVE-2012-1889 HIGH POC
8.8
CVE-2012-0507 CRITICAL POC
9.8
CVE-2014-1761 HIGH POC
7.8
CVE-2015-5122 CRITICAL POC
9.8
CVE-2011-0609 HIGH POC
7.8

References

Advisories & patches
PATCH https://cert-portal.siemens.com/productcert/pdf/ssa-390195.pdf PATCH https://github.com/LibVNC/libvncserver/commit/38e98ee61d74f5f5ab4aa4c77146faad1962d6d0 REF http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00033.html REF http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00055.html REF http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00066.html 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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