Bug 2520660 (CVE-2026-63382)

Summary:	CVE-2026-63382 libevent: libevent: Multiple HTTP Parser Bugs Enable Request Smuggling
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in libevent. The evhttp parser in libevent's http.c component inconsistently handles HTTP Transfer-Encoding headers and chunked framing. This inconsistency allows an unauthenticated remote attacker to desynchronize request boundaries when libevent is used behind a proxy. Successful exploitation could lead to request smuggling, potentially bypassing access controls or poisoning caches.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2527748
Bug Blocks:

Description OSIDB Bzimport 2026-08-20 18:05:06 UTC

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.

Comment 3 Jon Orris 2026-09-16 11:09:54 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:67908 https://access.redhat.com/errata/RHSA-2026:67908

Comment 4 Jon Orris 2026-09-16 11:48:39 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:67909 https://access.redhat.com/errata/RHSA-2026:67909

Comment 5 Jon Orris 2026-09-16 12:59:37 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:67910 https://access.redhat.com/errata/RHSA-2026:67910