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TI-2021-18987 Aliases CVE-2021-42785GHSA-7q87-cj95-29mc

Buffer Overflow in tvnviewer.exe via Crafted Packet in TightVNC Viewer 2.8.59

Priority MEDIUM 47CWE-120Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
No fix listed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-120 and the CVSS impact.

Summary

Buffer Overflow vulnerability in tvnviewer.exe of TightVNC Viewer allows a remote attacker to execute arbitrary instructions via a crafted FramebufferUpdate packet from a VNC server.

Why it matters now

EPSS 0.02342 83rd percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
GlavSoftTightVNC Viewer2.8.59 – 2.8.59—No fix listedCNA
  • TightVNC Viewer VendorGlavSoft Affected 2.8.59 – 2.8.59 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:tightvnc:tightvnc:*:*:*:*:*:*:*:*up to 2.8.59VulnerableTightvnc
  • cpe:2.3:a:tightvnc:tightvnc:*:*:*:*:*:*:*:* Versions up to 2.8.59 Vulnerable ·Tightvnc

Remediation

No fixed version listed by the sources yet.

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-42785
  2. 2026-10-03 Alias added: GHSA-7q87-cj95-29mc

References

Advisory 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-2026-69578 Out-of-bounds read in TightVNC Viewer ZRLE palette decoding CVSS 3.1HIGH 7.1
  • 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