CVE-2026-50538

Publication date 15 June 2026

Last updated 2 September 2026

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

8.8 · High

Score breakdown

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.

Status

Package Ubuntu Release Status
libvncserver 26.04 LTS resolute
Fixed 0.9.15+dfsg-3ubuntu0.2
25.10 questing
Fixed 0.9.15+dfsg-1ubuntu0.2
24.04 LTS noble
Fixed 0.9.14+dfsg-1ubuntu0.2
22.04 LTS jammy
Fixed 0.9.13+dfsg-3ubuntu0.2
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
vino 26.04 LTS resolute Not in release
25.10 questing Ignored end of life, was needs-triage
24.04 LTS noble
Needs evaluation
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
x11vnc 26.04 LTS resolute
Needs evaluation
25.10 questing Ignored end of life, was needs-triage
24.04 LTS noble
Needs evaluation
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
14.04 LTS trusty
Needs evaluation
veyon 26.04 LTS resolute
Needs evaluation
25.10 questing Ignored end of life, was needs-triage
24.04 LTS noble
Needs evaluation
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
italc 26.04 LTS resolute Not in release
25.10 questing Not in release
24.04 LTS noble Not in release
22.04 LTS jammy Not in release
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
tightvnc 26.04 LTS resolute
Needs evaluation
25.10 questing Ignored end of life, was needs-triage
24.04 LTS noble
Needs evaluation
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
14.04 LTS trusty
Needs evaluation

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
libvncserver

Severity score breakdown

CVSS version: CVSS v3.0

Base score 8.8 · High

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

References

Related Ubuntu Security Notices (USN)

    • USN-8494-1
    • LibVNCServer vulnerability
    • 2 July 2026

Other references

Access our resources on patching vulnerabilities