CVE-2026-44988

Name	CVE-2026-44988
Description	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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1138174

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
libvncserver (PTS)	bullseye	0.9.13+dfsg-2+deb11u1	vulnerable
	bookworm	0.9.14+dfsg-1+deb12u1	vulnerable
	trixie	0.9.15+dfsg-1+deb13u1	vulnerable
	forky	0.9.15+dfsg-5	fixed
	sid	0.9.15+dfsg-6	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
libvncserver	source	(unstable)	0.9.15+dfsg-5			1138174

Notes

[trixie] - libvncserver <no-dsa> (Minor issue)
https://github.com/LibVNC/libvncserver/security/advisories/GHSA-jcc5-8wj4-7c58
https://github.com/LibVNC/libvncserver/commit/5b270544b85233668b98161323297d418a8f5fd1