Out-of-bounds Write Affecting libvncserver package, versions <0.9.15+dfsg-3ubuntu0.1


Severity

Recommended
medium

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.44% (36th percentile)

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  • Snyk IDSNYK-UBUNTU2604-LIBVNCSERVER-17092630
  • published24 Jun 2026
  • disclosed27 May 2026

Introduced: 27 May 2026

CVE-2026-44988  (opens in a new tab)
CWE-787  (opens in a new tab)

How to fix?

Upgrade Ubuntu:26.04 libvncserver to version 0.9.15+dfsg-3ubuntu0.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream libvncserver package and not the libvncserver package as distributed by Ubuntu. See How to fix? for Ubuntu:26.04 relevant fixed versions and status.

LibVNCClient is a library for easy implementation of a VNC client. In 0.9.15 and earlier, LibVNCClient's Tight encoding decoder uses fixed-size 2048-pixel scratch buffers for the Gradient filter, but it does not reject Tight rectangles whose width is larger than 2048 pixels. A malicious VNC server can send a crafted FramebufferUpdate rectangle using Tight encoding with NoZlib | ExplicitFilter and the Gradient filter. When a LibVNCClient-based client connects, the client processes the server-controlled rectangle width and writes beyond fixed-size Gradient buffers. This vulnerability is fixed with commit 5b270544b85233668b98161323297d418a8f5fd1.

CVSS Base Scores

version 3.1