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CVE-2026-50538

8.8 · HIGH

LibVNCClient is a library for easy implementation of a VNC client.

Published Aug 21, 2026CWE-122EPSS 0.40%

Overview

CVE-2026-50538 is a high-severity vulnerability. It was published on August 21, 2026 and has a CVSS 3.1 base score of 8.8 (HIGH).

This vulnerability has a CVSS 3.1 base score of 8.8, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/LibVNC/libvncserver/commit/540332be3e0acc566fa64da6f1b4680c72c724ddGitHubgithub.com/LibVNC/libvncserver/security/advisories/GHSA-v9pm-47h4-jcq8GitHubgithub.com/LibVNC/libvncserver/security/advisories/GHSA-v9pm-47h4-jcq8

How CyberStrike helps

Frequently asked questions

What is CVE-2026-50538?

CVE-2026-50538 is a high-severity vulnerability. It was published on August 21, 2026 and has a CVSS 3.1 base score of 8.8 (HIGH).

How severe is CVE-2026-50538?

This vulnerability has a CVSS 3.1 base score of 8.8, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-50538?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-50538?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-50538 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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