Vulnerability · Published Aug 20, 2026 · Assigned by GitHub_M
CVE-2026-63382libevent evhttp: Multiple HTTP Parser Bugs Enable Request Smuggling
Critical 9.2
In plain English
A critical-severity security flaw in libevent from libevent. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 56% 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, the libevent evhttp parser in http.c inconsistently handles duplicate Transfer-Encoding headers, comma-separated Transfer-Encoding values, and bare line feeds in chunked framing. evhttp_find_header can select only the first header, evhttp_check_transfer_encoding_ was absent so the previous whole-string comparison fails to recognize valid lists ending in chunked, and evhttp_handle_chunked_read uses EVBUFFER_EOL_CRLF rather than EVBUFFER_EOL_CRLF_STRICT, accepting bare LF chunk terminators. When libevent is deployed behind a proxy that frames the same request differently, an unauthenticated remote attacker can desynchronize request boundaries and smuggle a second request, potentially bypassing access controls or poisoning caches. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.
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-2026-63382 |
| Debian:13 | libevent | 2.1.13-stable-1~deb13u1 | DEBIAN-CVE-2026-63382 |
| Debian:14 | libevent | 2.1.13-stable-1 | DEBIAN-CVE-2026-63382 |
| 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-2026-63382 |
| 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-2026-63382 |
| 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-2026-63382 |
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-q39v-w2g7-gr8j x_refsource_CONFIRM
- https://github.com/libevent/libevent/commit/10abb34b8dc3e1184de315dd261ce4b77563cda6 x_refsource_MISC
- https://github.com/libevent/libevent/commit/5119ceb00557bf007f9065709e852686f3c0bb6e x_refsource_MISC
- https://github.com/libevent/libevent/commit/83ba67373032334559b82409db035dd8c3cc1660 x_refsource_MISC
- https://github.com/libevent/libevent/commit/ac38703b2d312200c4f967f02936af0118d384a0 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