# CVE-2026-63379: Libevent: HTTP Header smuggling CVE-2026-63379 is fixed in 5 products on 1 platform, first by DEBIAN-CVE-2026-63379, released August 21, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-63379 - Priority: High - CVSS: 8.6 (Moderate) - EPSS: 0.0052 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Aug 20, 2026 - Weakness: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63379 ## Description 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. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | libevent Debian 12.15 (bookworm) | 2.1.12-stable-8+deb12u1 | [DEBIAN-CVE-2026-63379](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63379.md) | Aug 21, 2026 | | Linux | libevent Debian 13.5 (trixie) | 2.1.13-stable-1~deb13u1 | [DEBIAN-CVE-2026-63379](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63379.md) | Aug 21, 2026 | | Linux | libevent Debian 14 | 2.1.13-stable-1 | [DEBIAN-CVE-2026-63379](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63379.md) | Aug 21, 2026 | | Linux | libevent Fedora 43 | 2.1.13-1.fc43 | [FEDORA-2026-728DD9F704](https://patchblox.com/security/data/fix/linux/fedora-2026-728dd9f704.md) | Sep 7, 2026 | | Linux | libevent RHEL 10 | 2.1.13-1.el10_2 | [RHSA-2026:67909](https://patchblox.com/security/data/fix/linux/rhsa-2026-67909.md) | Sep 17, 2026 | | Linux | libevent RHEL 9 | 0:2.1.13-1.el9_8 | [RHSA-2026:67910](https://patchblox.com/security/data/fix/linux/rhsa-2026-67910.md) | Sep 19, 2026 | | Linux | libevent almalinux 10 | 2.1.13-1.el10_2 | [ALSA-2026:67909](https://patchblox.com/security/data/fix/linux/alsa-2026-67909.md) | Sep 16, 2026 | | Linux | libevent almalinux 9 | 2.1.13-1.el9_8 | [ALSA-2026:67910](https://patchblox.com/security/data/fix/linux/alsa-2026-67910.md) | Sep 16, 2026 | | Linux | libevent ol 10 | 0:2.1.13-1.el10_2 | [ELSA-2026-67909](https://patchblox.com/security/data/fix/linux/elsa-2026-67909.md) | Sep 16, 2026 | | Linux | libevent ol 9 | 0:2.1.13-1.el9_8 | [ELSA-2026-67910](https://patchblox.com/security/data/fix/linux/elsa-2026-67910.md) | Sep 16, 2026 | | Linux | libevent rocky 10 | 0:2.1.13-1.el10_2 | [RLSA-2026:67909](https://patchblox.com/security/data/fix/linux/rlsa-2026-67909.md) | Sep 17, 2026 | | Linux | libevent rocky 9 | 0:2.1.13-1.el9_8 | [RLSA-2026:67910](https://patchblox.com/security/data/fix/linux/rlsa-2026-67910.md) | Sep 17, 2026 | | Linux | libevent-debuginfo Fedora 43 | 2.1.13-1.fc43 | [FEDORA-2026-728DD9F704](https://patchblox.com/security/data/fix/linux/fedora-2026-728dd9f704.md) | Sep 7, 2026 | | Linux | libevent-debugsource Fedora 43 | 2.1.13-1.fc43 | [FEDORA-2026-728DD9F704](https://patchblox.com/security/data/fix/linux/fedora-2026-728dd9f704.md) | Sep 7, 2026 | | Linux | libevent-devel Fedora 43 | 2.1.13-1.fc43 | [FEDORA-2026-728DD9F704](https://patchblox.com/security/data/fix/linux/fedora-2026-728dd9f704.md) | Sep 7, 2026 | | Linux | libevent-devel RHEL 9 | 0:2.1.13-1.el9_8 | [RHSA-2026:67910](https://patchblox.com/security/data/fix/linux/rhsa-2026-67910.md) | Sep 19, 2026 | | Linux | libevent-devel almalinux 10 | 2.1.13-1.el10_2 | [ALSA-2026:67909](https://patchblox.com/security/data/fix/linux/alsa-2026-67909.md) | Sep 16, 2026 | | Linux | libevent-devel almalinux 9 | 2.1.13-1.el9_8 | [ALSA-2026:67910](https://patchblox.com/security/data/fix/linux/alsa-2026-67910.md) | Sep 16, 2026 | | Linux | libevent-devel ol 10 | 0:2.1.13-1.el10_2 | [ELSA-2026-67909](https://patchblox.com/security/data/fix/linux/elsa-2026-67909.md) | Sep 16, 2026 | | Linux | libevent-devel ol 9 | 0:2.1.13-1.el9_8 | [ELSA-2026-67910](https://patchblox.com/security/data/fix/linux/elsa-2026-67910.md) | Sep 16, 2026 | | Linux | libevent-doc Fedora 43 | 2.1.13-1.fc43 | [FEDORA-2026-728DD9F704](https://patchblox.com/security/data/fix/linux/fedora-2026-728dd9f704.md) | Sep 7, 2026 | | Linux | libevent-doc RHEL 9 | 0:2.1.13-1.el9_8 | [RHSA-2026:67910](https://patchblox.com/security/data/fix/linux/rhsa-2026-67910.md) | Sep 19, 2026 | | Linux | libevent-doc almalinux 10 | 2.1.13-1.el10_2 | [ALSA-2026:67909](https://patchblox.com/security/data/fix/linux/alsa-2026-67909.md) | Sep 16, 2026 | | Linux | libevent-doc almalinux 9 | 2.1.13-1.el9_8 | [ALSA-2026:67910](https://patchblox.com/security/data/fix/linux/alsa-2026-67910.md) | Sep 16, 2026 | | Linux | libevent-doc ol 10 | 0:2.1.13-1.el10_2 | [ELSA-2026-67909](https://patchblox.com/security/data/fix/linux/elsa-2026-67909.md) | Sep 16, 2026 | | Linux | libevent-doc ol 9 | 0:2.1.13-1.el9_8 | [ELSA-2026-67910](https://patchblox.com/security/data/fix/linux/elsa-2026-67910.md) | Sep 16, 2026 | --- Data as of 2026-11-09T13:31:49Z UTC. 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