What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-08 · updated 2026-10-08
• Weakness: CWE-125

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 products

• GlavSoft TightVNC: before 2.8.88 — fixed in 2.8.88

How to fix

Upgrade to a fixed version: GlavSoft TightVNC 2.8.88. Check the vendor advisory for mitigations.

References

• https://sourceforge.net/p/vnc-tight/bugs/1657/
• https://www.tightvnc.com/whatsnew.php

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