CVE-2026-63382

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.

CVSS 4.0

9.2CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:N

EPSS

0.8% chance of exploitation in the next 30 days; higher than 55% of CVEs (scores of 2026-10-25)

CWE

CWE-444

Published

2026-08-20

Modified

2026-10-26

Record from

the NVD, synced 2026-10-26

References

• 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

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