Libevent up to 2.1.12 Evhttp Parser http.c evhttp_find_header crlf injection

Summaryinfo

A vulnerability was found in Libevent up to 2.1.12 and classified as critical. Affected is the function evhttp_find_header of the file http.c of the component Evhttp Parser. The manipulation results in crlf injection. This vulnerability is known as CVE-2026-63382. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability was found in Libevent up to 2.1.12. It has been classified as critical. Affected is the function evhttp_find_header of the file http.c of the component Evhttp Parser. The manipulation with an unknown input leads to a crlf injection vulnerability. CWE is classifying the issue as CWE-93. The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-63382 since 07/16/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit.

Upgrading to version 2.1.13 or 2.2.2-alpha eliminates this vulnerability.

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Productinfo

Name

• Libevent

Version

• 2.1.0
• 2.1.1
• 2.1.2
• 2.1.3
• 2.1.4
• 2.1.5
• 2.1.6
• 2.1.7
• 2.1.8
• 2.1.9
• 2.1.10
• 2.1.11
• 2.1.12

Website

• Product: https://github.com/libevent/libevent/

CPE 2.3info

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CPE 2.2info

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