CVE-2026-128321
Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow vulnerability
Tight JPEG decoding in TightVNC and UltraVNC viewers contains a heap-based buffer overflow because an attacker-controlled framebuffer rectangle width is not validated against a fixed-size decoding buffer. A malicious VNC server can cause an out-of-bounds heap write when a user connects, resulting in application crash and potentially other memory-corruption impacts.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| UltraVNC UltraVNC |
≥ 1.8.2.4; ≤ 1.8.2.6 (affected, custom) | CNA: certcc |
| TightVNC Glavsoft (TightVNC) |
≥ 1.3.10; ≤ 1.3.10 (affected, custom) | CNA: certcc |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
No CVSS assessment reported. An unscored record is not a low-severity determination.
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://www.tightvnc.com/CNA: certcc
- https://github.com/ultravnc/ultravncCNA: certcc
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