UltraVNC revision 1198 has a buffer underflow vulnerability in VNC client code, which can potentially result in code execution. This attack appears to be exploitable via network connectivity. This vulnerability has been fixed in revision 1199.
Severity
CVSS 3.0
9.8 critical
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
2.9% chance of exploitation in the next 30 days; higher than 86% of CVEs (scores of 2026-10-31)