Vulnerability · Published Aug 20, 2026 · Assigned by GitHub_M
CVE-2026-63385Libevent: HTTP header handling bugs create risk of access control bypass.
Critical 9.2
In plain English
A critical-severity security flaw in libevent from libevent. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.3% (higher than 70% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | libevent | 2.1.13-1.el10_2 | ALSA-2026:67909 |
| AlmaLinux:8 | libevent | 2.1.8-11.el8_10 | ALSA-2026:67908 |
| AlmaLinux:9 | libevent | 2.1.13-1.el9_8 | ALSA-2026:67910 |
| AlmaLinux:10 | libevent-devel | 2.1.13-1.el10_2 | ALSA-2026:67909 |
| AlmaLinux:8 | libevent-devel | 2.1.8-11.el8_10 | ALSA-2026:67908 |
| AlmaLinux:9 | libevent-devel | 2.1.13-1.el9_8 | ALSA-2026:67910 |
| AlmaLinux:10 | libevent-doc | 2.1.13-1.el10_2 | ALSA-2026:67909 |
| AlmaLinux:8 | libevent-doc | 2.1.8-11.el8_10 | ALSA-2026:67908 |
| AlmaLinux:9 | libevent-doc | 2.1.13-1.el9_8 | ALSA-2026:67910 |
| Debian:12 | libevent | 2.1.12-stable-8+deb12u1 | DEBIAN-CVE-2026-63385 |
| Debian:13 | libevent | 2.1.13-stable-1~deb13u1 | DEBIAN-CVE-2026-63385 |
| Debian:14 | libevent | 2.1.13-stable-1 | DEBIAN-CVE-2026-63385 |
| Rocky Linux:10 | libevent | 0:2.1.13-1.el10_2 | RLSA-2026:67909 |
| Rocky Linux:8 | libevent | 0:2.1.8-11.el8_10 | RLSA-2026:67908 |
| Rocky Linux:9 | libevent | 0:2.1.13-1.el9_8 | RLSA-2026:67910 |
| Ubuntu:22.04:LTS | libevent | 2.1.12-stable-1ubuntu0.1 | UBUNTU-CVE-2026-63385 |
| Ubuntu:22.04:LTS | libevent | 2.1.12-stable-1ubuntu0.1 | USN-8710-1 |
| Ubuntu:24.04:LTS | libevent | 2.1.12-stable-9ubuntu2.1 | USN-8710-1 |
| Ubuntu:24.04:LTS | libevent | 2.1.12-stable-9ubuntu2.1 | UBUNTU-CVE-2026-63385 |
| Ubuntu:26.04:LTS | libevent | 2.1.12-stable-10ubuntu0.1 | USN-8710-1 |
| Ubuntu:26.04:LTS | libevent | 2.1.12-stable-10ubuntu0.1 | UBUNTU-CVE-2026-63385 |
Affected products (as reported)
Weakness: CWE-444 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:N
References
- https://github.com/libevent/libevent/security/advisories/GHSA-jcwh-pvf2-73p2 x_refsource_CONFIRM
- https://github.com/libevent/libevent/commit/758be0c0f69c1934ef9a84ab39e9f9e5fde2e6d0 x_refsource_MISC
- https://github.com/libevent/libevent/commit/9170dd35e64714613e8d13b290587cfc28e258e2 x_refsource_MISC
- https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable x_refsource_MISC
- https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha x_refsource_MISC