Critical (9.8). EPSS 4.2% chance of exploitation in the next 30 days.
An issue was discovered in libX11 through 1.6.5. The function XListExtensions in ListExt.c is vulnerable to an off-by-one error caused by malicious server responses, leading to DoS or possibly unspecified other impact.
Severity
CVSS 3.1
9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
4.2% chance of exploitation in the next 30 days; higher than 90% of CVEs (scores of 2026-10-31)