CVE-2026-63385: Libevent

Critical severity, CVSS 9.2. EPSS: 0.6% chance of exploitation in the next 30 days.

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has two HTTP parsing weaknesses in http.c. evhttp_decode_uri_internal decodes percent-encoded %00 bytes into literal NUL characters, which can cause downstream C string operations to truncate a path and bypass validation performed on a different representation. evhttp_header_is_valid_value also accepts obsolete line folding in header values containing carriage return or line feed characters, allowing a proxy and libevent to interpret headers differently and enabling header injection or access control bypass. The CRLF header acceptance is fixed in versions 2.1.13 and 2.2.2-alpha, but the reviewed patches do not clearly remediate the URI NUL-truncation condition.

Affected products

• Libevent Libevent: from 2.2.0-alpha, before 2.2.2-alpha (fixed in 2.2.2-alpha); before 2.1.13 (fixed in 2.1.13)

Published 2026-08-20. Last modified 2026-09-09.