Vulnerability 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.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/LibVNC/libvncserver/commit/540332be3e0acc566fa64da6f1b4680c72
- https://github.com/LibVNC/libvncserver/security/advisories/GHSA-v9pm-47h4-jcq8
FAQ
What is CVE-2026-50538?
CVE-2026-50538 is a vulnerability with a CVSS score of 8.8 (HIGH). 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 attac...
How severe is CVE-2026-50538?
CVE-2026-50538 has been rated HIGH with a CVSS base score of 8.8/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-50538?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.