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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-107611
StatePUBLISHED
Assignersecurin
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-08 14:16:49 UTC
Updated2026-10-08 15:17:45 UTC
DescriptionAn 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.

Risk And Classification

Primary CVSS: v3.1 7.1 HIGH from 33c584b5-0579-4c06-b2a0-8d8329fcab9c

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H

Problem Types: CWE-125 | CWE-125 CWE-125 Out-of-bounds Read

VersionSourceTypeScoreSeverityVector
3.133c584b5-0579-4c06-b2a0-8d8329fcab9cSecondary7.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
3.1CNACVSS7.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA GlavSoft TightVNC affected 2.8.88 custom Windows

References

ReferenceSourceLinkTags
sourceforge.net/p/vnc-tight/bugs/1657 33c584b5-0579-4c06-b2a0-8d8329fcab9c sourceforge.net
www.tightvnc.com/whatsnew.php 33c584b5-0579-4c06-b2a0-8d8329fcab9c www.tightvnc.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Arjun Basnet from Securin (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-05-30T00:00:00.000ZReported to GlavSoft
CNA2026-06-02T00:00:00.000ZVendor acknowledged
CNA2026-06-19T00:00:00.000ZTightVNC 2.8.88 released with fix

Solutions

CNA: Upgrade TightVNC for Windows to version 2.8.88 or later.

Workarounds

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

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