CVE-2026-50538
libvncclient Tight decoder has an attacker-controlled heap out-of-bounds write
Description
LibVNCClient is a library for easy implementation of a VNC client. In versions 0.9.12 through 0.9.15, a malicious (or man-in-the-middle) VNC server can force a connecting `libvncclient` to write attacker-controlled data past the end of its framebuffer. This is an out-of-bounds heap write with attacker-controlled length, contents, and offset. It needs no authentication (the attacker is the server), works in a default build with default settings, and fires from a single `FramebufferUpdate` the moment the victim connects. It crashes any client unconditionally (denial of service); we also demonstrated it overwriting an application callback pointer and redirecting execution to attacker-chosen code (code execution) under the default configuration. Commit 540332be3e0acc566fa64da6f1b4680c72c724dd patches the issue.
INFO
Published Date :
Aug. 21, 2026, 9:16 p.m.
Last Modified :
Aug. 21, 2026, 9:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-50538
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | MITRE-CVE |
Solution
- Update LibVNCClient to version 0.9.16 or later.
- Apply commit 540332be3e0acc566fa64da6f1b4680c72c724dd.
- Rebuild the application with the patched library.
- Restart the application after updating.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-50538.
| URL | Resource |
|---|---|
| https://github.com/LibVNC/libvncserver/commit/540332be3e0acc566fa64da6f1b4680c72c724dd | |
| https://github.com/LibVNC/libvncserver/security/advisories/GHSA-v9pm-47h4-jcq8 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-50538 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-50538
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-50538 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-50538 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Aug. 21, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'LibVNC', 'product': 'libvncserver', 'versions': [{'status': 'affected', 'version': '>= 0.9.12, <= 0.9.15'}]}] Added Description LibVNCClient is a library for easy implementation of a VNC client. In versions 0.9.12 through 0.9.15, a malicious (or man-in-the-middle) VNC server can force a connecting `libvncclient` to write attacker-controlled data past the end of its framebuffer. This is an out-of-bounds heap write with attacker-controlled length, contents, and offset. It needs no authentication (the attacker is the server), works in a default build with default settings, and fires from a single `FramebufferUpdate` the moment the victim connects. It crashes any client unconditionally (denial of service); we also demonstrated it overwriting an application callback pointer and redirecting execution to attacker-chosen code (code execution) under the default configuration. Commit 540332be3e0acc566fa64da6f1b4680c72c724dd patches the issue. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Added CWE CWE-787 Added CWE CWE-122 Added Reference https://github.com/LibVNC/libvncserver/commit/540332be3e0acc566fa64da6f1b4680c72c724dd Added Reference https://github.com/LibVNC/libvncserver/security/advisories/GHSA-v9pm-47h4-jcq8