Vulnerability · Published Oct 8, 2026 · Assigned by securin

CVE-2026-107611Out-of-bounds read in TightVNC Viewer ZRLE palette decoding

High 7.1

In plain English

A high-severity out-of-bounds read in TightVNC from GlavSoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 15% of all known vulnerabilities).

Severity (CVSS 3.1)7.1High

Exploit odds (30 days)0.2%top 85.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

An out-of-bounds read vulnerability in the ZRLE decoder of GlavSoft TightVNC Viewer for Windows before 2.8.88 allows a malicious or compromised VNC server to read heap memory beyond the palette allocation and crash the viewer by sending ZRLE-encoded tiles whose palette indices exceed the declared palette size. readPaletteRleTile() and readPackedPaletteTile() use the attacker-supplied index to look up colours without validating it against the palette size; out-of-bounds heap data is copied into the framebuffer (garbled display) or the read faults, terminating the viewer.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Ubuntu:22.04:LTS	tightvnc	no fix listed	UBUNTU-CVE-2026-107611
Ubuntu:24.04:LTS	tightvnc	no fix listed	UBUNTU-CVE-2026-107611
Ubuntu:26.04:LTS	tightvnc	no fix listed	UBUNTU-CVE-2026-107611

Affected products (as reported)

Vendor	Product	Versions
GlavSoft	TightVNC	0 – before 2.8.88

Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H

References

TightVNC bug #1657 issue-tracking
TightVNC release notes (2.8.88) release-notes, patch