CVE-2026-63379Libevent: HTTP Header smuggling
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent processes chunked HTTP trailers in http.c through evhttp_read_trailer and merges them into request headers. The fix introduces evhttp_parse_headers_impl_ and a temporary trailer header list. An unauthenticated remote attacker can place security-sensitive fields in trailers so that an upstream proxy and the libevent application interpret different effective headers, enabling header smuggling, authorization bypass, proxy-header spoofing, or cache poisoning. The fix parses trailers into a temporary header list and discards them instead of merging them into req->input_headers. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.
- CVSS
- 6.3 MEDIUM (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
- Weakness (CWE)
- CWE-444
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Awaiting Analysis
- Record last updated
- Aug 25, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
libevent libevent libevent:libevent (from the name) | before 2.1.13; from 2.2.0-alpha, < 2.2.2-alpha | CNA record |
References
- https://github.com/libevent/libevent/security/advisories/GHSA-2gmv-p5m7-98p6x-refsource-confirm
- https://github.com/libevent/libevent/commit/87e8e44fa774e9677b089b1a5114ee68aefa1636x-refsource-misc
- https://github.com/libevent/libevent/commit/b847071141b3827900d536594ec9045eb0a4c485x-refsource-misc
- https://github.com/libevent/libevent/releases/tag/release-2.1.13-stablex-refsource-misc
- https://github.com/libevent/libevent/releases/tag/release-2.2.2-alphax-refsource-misc
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.