CVE-2026-63382
CriticalCVSS 9.2Summary
Libevent before versions 2.1.13 and 2.2.2-alpha inconsistently handles duplicate Transfer-Encoding headers, comma-separated values, and bare line feeds in chunked framing. This can lead to request desynchronization and request smuggling by an unauthenticated remote attacker when deployed behind a proxy.
Risk Assessment
An attacker may bypass access controls or poison caches, potentially leading to unauthorized data access or system integrity compromise.
Recommendation
Update Libevent to version 2.1.13 or 2.2.2-alpha (or later) which includes the fix.
Original NVD description (English source)
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.