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.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
libevent libevent
>= 2.2.0-alpha, < 2.2.2-alphaaffected< 2.1.13affected
References
- https://github.com/libevent/libevent/security/advisories/GHSA-q39v-w2g7-gr8j ↗
- https://github.com/libevent/libevent/commit/10abb34b8dc3e1184de315dd261ce4b77563cda6 ↗
- https://github.com/libevent/libevent/commit/5119ceb00557bf007f9065709e852686f3c0bb6e ↗
- https://github.com/libevent/libevent/commit/83ba67373032334559b82409db035dd8c3cc1660 ↗
- https://github.com/libevent/libevent/commit/ac38703b2d312200c4f967f02936af0118d384a0 ↗
- https://github.com/libevent/libevent/releases/tag/release-2.1.13-stable ↗
- https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha ↗