Libevent: HTTP header handling bugs create risk of access control bypass.

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63385
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-20 18:16:36 UTC
Updated2026-08-20 18:16:36 UTC
DescriptionLibevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has two HTTP parsing weaknesses in http.c. evhttp_decode_uri_internal decodes percent-encoded %00 bytes into literal NUL characters, which can cause downstream C string operations to truncate a path and bypass validation performed on a different representation. evhttp_header_is_valid_value also accepts obsolete line folding in header values containing carriage return or line feed characters, allowing a proxy and libevent to interpret headers differently and enabling header injection or access control bypass. The CRLF header acceptance is fixed in versions 2.1.13 and 2.2.2-alpha, but the reviewed patches do not clearly remediate the URI NUL-truncation condition.

Risk And Classification

Primary CVSS: v4.0 9.2 CRITICAL from [email protected]

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-444 | CWE-444 CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary9.2CRITICALCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:N/E:X/C...
4.0CNADECLARED9.2CRITICALCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
None
User Interaction
None
Confidentiality
High
Integrity
High
Availability
Low
Sub Conf.
Low
Sub Integrity
Low
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Libevent Libevent affected >= 2.2.0-alpha, < 2.2.2-alpha Not specified
CNA Libevent Libevent affected < 2.1.13 Not specified

References

ReferenceSourceLinkTags
github.com/libevent/libevent/commit/758be0c0f69c1934ef9a84ab39e9f9e5fde2... [email protected] github.com
github.com/libevent/libevent/security/advisories/GHSA-jcwh-pvf2-73p2 [email protected] github.com
github.com/libevent/libevent/releases/tag/release-2.1.13-stable [email protected] github.com
github.com/libevent/libevent/releases/tag/release-2.2.2-alpha [email protected] github.com
github.com/libevent/libevent/commit/9170dd35e64714613e8d13b290587cfc28e2... [email protected] github.com
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