CVE-2026-128321: UltraVNC · Heap-based Buffer Overflow
Affects UltraVNCSource CVE Database V5
Not known to be exploited.
Data as of 13 Nov 2026, 01:04 UTC
Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD
Thin evidence
One scorer or noneExploitation evidence
Disclosed: evidence found.
CVE published 13 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| UltraVNCUltraVNC | Affected
| Fixed in– |
| Glavsoft (TightVNC)TightVNC | Affected
| Fixed in– |
GitHubultravnc/ultravncpkg:github/ultravnc/ultravncOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Users should exercise caution when connecting to untrusted VNC servers. Monitor the vendor's advisory channels for updates and apply any future patches promptly. Since this is a client-side vulnerability, limiting connections to trusted servers reduces exposure.
Description
A heap-based buffer overflow vulnerability exists in the Tight JPEG decoding component of TightVNC and UltraVNC viewers. This occurs because the width of a framebuffer rectangle, controlled by an attacker, is not validated against a fixed-size decoding buffer. A malicious VNC server can exploit this flaw to cause an out-of-bounds heap write when a user connects, leading to application crashes and potential memory corruption.