High severity · published Oct 8, 2026
CVE-2026-107611
Out-of-bounds read in TightVNC Viewer ZRLE palette decoding
7.1
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 15% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
TI
TightVNC · GlavSoft
before 2.8.88 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-107611
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-107611
issue-tracking
https://sourceforge.net/p/vnc-tight/bugs/1657/
release-notes
https://www.tightvnc.com/whatsnew.php
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