CVE-2026-107611

Out-of-bounds read in TightVNC Viewer ZRLE palette decoding

Published Oct 8, 2026 CVSS 3.1 · 7.1 High EPSS < 1% KEV · Not listed
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.

Remediation

Vendor Solution

Upgrade TightVNC for Windows to version 2.8.88 or later.


Vendor Workaround

Connect only to trusted VNC servers until the viewer is upgraded.

Tracking

Sign in to view the affected projects.

Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Glavsoft
Glavsoft tightvnc
Vendors & Products Glavsoft
Glavsoft tightvnc
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Out-of-bounds read in TightVNC Viewer ZRLE palette decoding
Weaknesses CWE-125
References
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
securin
Published
Updated
Oct 8, 2026, 2:03 PM
Reserved
Oct 8, 2026, 1:23 PM
Status
Awaiting Analysis
Published
Oct 8, 2026, 2:16 PM
Modified
Oct 8, 2026, 9:10 PM