CVE-2026-63382

01/Description

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.

02/References8

• github.com/libevent/libevent/commit/10abb34b8dc3e1184de315dd261…
• github.com/libevent/libevent/commit/5119ceb00557bf007f9065709e8…
• github.com/libevent/libevent/commit/83ba67373032334559b82409db0…
• github.com/libevent/libevent/commit/ac38703b2d312200c4f967f0293…
• github.com/libevent/libevent/releases/tag/release-2.1.13-stable
• github.com/libevent/libevent/releases/tag/release-2.2.2-alpha
• github.com/libevent/libevent/security/advisories/GHSA-q39v-w2g7…
• github.com/libevent/libevent/security/advisories/GHSA-q39v-w2g7…