HTTP Request Smuggling Affecting libevent package, versions <2.1.12-stable-10+e1


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.71% (52nd percentile)

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  • Snyk IDSNYK-ECHOLATEST-LIBEVENT-19166016
  • published22 Aug 2026
  • disclosed20 Aug 2026

Introduced: 20 Aug 2026

CVE-2026-63379  (opens in a new tab)
CWE-444  (opens in a new tab)

How to fix?

Upgrade Echo:latest libevent to version 2.1.12-stable-10+e1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream libevent package and not the libevent package as distributed by Echo. See How to fix? for Echo:latest relevant fixed versions and status.

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 Base Scores

version 3.1