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CVE-2026-63379

CVE-2026-63379 · Libevent: HTTP Header smuggling

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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 · EPSS 0.7% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • libevent

    Versions
    • < 2.1.13: Affected
    • >= 2.2.0-alpha, < 2.2.2-alpha: Affected

    No fix published

  • libevent Debian:12

    Versions
    • 2.1.12-stable-8
    Affected ranges
    • ECOSYSTEM: < 2.1.12-stable-8+deb12u1

    Update to 2.1.12-stable-8+deb12u1

  • libevent Debian:13

    Versions
    • 2.1.12-stable-10
    Affected ranges
    • ECOSYSTEM: < 2.1.13-stable-1~deb13u1

    Update to 2.1.13-stable-1~deb13u1

  • libevent Debian:14

    Versions
    • 2.1.12-stable-10
    • 2.1.13-stable-1~deb13u1
    Affected ranges
    • ECOSYSTEM: < 2.1.13-stable-1

    Update to 2.1.13-stable-1

  • libevent Ubuntu:Pro:14.04:LTS

    Versions
    • 2.0.21-stable-1
    • 2.0.21-stable-1ubuntu1
    • 2.0.21-stable-1ubuntu1.14.04.1
    • 2.0.21-stable-1ubuntu1.14.04.2
    • 2.0.21-stable-1ubuntu1.14.04.2+esm1
    • 2.0.21-stable-1ubuntu1.14.04.2+esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:Pro:16.04:LTS

    Versions
    • 2.0.21-stable-2
    • 2.0.21-stable-2ubuntu0.16.04.1
    • 2.0.21-stable-2ubuntu0.16.04.1+esm1
    • 2.0.21-stable-2ubuntu0.16.04.1+esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:Pro:18.04:LTS

    Versions
    • 2.1.8-stable-4
    • 2.1.8-stable-4build1
    • 2.1.8-stable-4ubuntu0.1~esm1
    • 2.1.8-stable-4ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:Pro:20.04:LTS

    Versions
    • 2.1.8-stable-4build1
    • 2.1.11-stable-1~exp0
    • 2.1.11-stable-1
    • 2.1.11-stable-1ubuntu0.1~esm1
    • 2.1.11-stable-1ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:22.04:LTS

    Versions
    • 2.1.12-stable-1
    • 2.1.12-stable-1build1
    • 2.1.12-stable-1build2
    • 2.1.12-stable-1build3
    • 2.1.12-stable-1ubuntu0.1
    • 2.1.12-stable-1ubuntu0.2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:24.04:LTS

    Versions
    • 2.1.12-stable-9
    • 2.1.12-stable-9ubuntu2
    • 2.1.12-stable-9ubuntu2.1
    • 2.1.12-stable-9ubuntu2.2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:26.10

    Versions
    • 2.1.12-stable-10build2
    • 2.1.13-stable-1build1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • libevent Ubuntu:26.04:LTS

    Versions
    • 2.1.12-stable-10build1
    • 2.1.12-stable-10build2
    • 2.1.12-stable-10ubuntu0.1
    • 2.1.12-stable-10ubuntu0.2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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