{"id":"CVE-2026-50538","title":"LibVNCClient is a library for easy implementation of a VNC client","summary":"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 i…","severity":"high","cvss":8.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","cwe":["CWE-122","CWE-787"],"published":"2026-08-21","updated":"2026-09-30","sourceUpdated":"2026-09-30T19:57:08.043","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-50538","references":[{"url":"https://github.com/LibVNC/libvncserver/commit/540332be3e0acc566fa64da6f1b4680c72c724dd","label":"security-advisories@github.com"},{"url":"https://github.com/LibVNC/libvncserver/security/advisories/GHSA-v9pm-47h4-jcq8","label":"security-advisories@github.com"},{"url":"https://github.com/LibVNC/libvncserver/security/advisories/GHSA-v9pm-47h4-jcq8","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"tags":["nvd"],"epss":0.00605,"epssPercentile":0.46983,"ingestedAt":"2026-09-30T20:23:19.469Z","slug":"CVE-2026-50538","body":"## Overview\n\nLibVNCClient 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\nis 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":49,"depthScoreParts":{"impact":48.4,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}