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TI-2026-69578 Aliases CVE-2026-107611GHSA-r575-8hw6-vfq3

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

Priority LOW 31CWE-125Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
Low · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

GlavSoft TightVNC Viewer for Windows before 2.8.88 contains an out-of-bounds read (CWE-125) in its ZRLE decoder. The decoder uses palette indices from the server without checking them against the palette size, so it reads heap memory past the palette allocation. A malicious or compromised VNC server can send crafted ZRLE tiles to crash the viewer or copy out-of-bounds heap data into the display.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

Description from the CNA

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00236 14th percentileScored 2026-11-07
Fix Fixed TightVNC (GlavSoft): 2.8.88

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
GlavSoftTightVNCbefore 2.8.882.8.88Patch availableCNA
  • TightVNC VendorGlavSoft Affected before 2.8.88 Fixed in 2.8.88 Patch available CNA

Remediation

Update GlavSoft TightVNC Viewer for Windows to version 2.8.88, the fixed version listed in the sources.

Written with Claude Haiku 5.5 from the sources below · 2026-10-29

  • Fix · CNA TightVNC (GlavSoft) Fixed in 2.8.88

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    GlavSoft TightVNC 2.8.88

    5 records Highest priority Priority LOW 5 LOW

    Other records, highest priority first

    • TI-2026-69582 DLL search order hijacking via screenhooks libraries in TightVNC ServerPriority LOW 35
    • TI-2026-69579 Incorrect permissions on TightVNC IPC shared memory in TightVNC ServerPriority LOW 35
    • TI-2026-69581 Integer underflow in TightVNC Server cursor shape trimmingPriority LOW 26
    Show all 5 records →

Timeline

  1. 2026-10-08 Threatist record created from CVE-2026-107611
  2. 2026-10-08 Alias added: GHSA-r575-8hw6-vfq3

References

Patch 1

Other 1

  • TI-2026-69582 DLL search order hijacking via screenhooks libraries in TightVNC Server CVSS 3.1HIGH 7.8
  • TI-2026-69579 Incorrect permissions on TightVNC IPC shared memory in TightVNC Server CVSS 3.1HIGH 7.8
  • TI-2026-69581 Integer underflow in TightVNC Server cursor shape trimming CVSS 3.1MEDIUM 6.1
  • TI-2026-69580 NULL pointer dereference in TightVNC Server Win8ScreenDriver crashes server CVSS 3.1MEDIUM 5.9

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences