CVE-2026-63385: Red Hat HTTP header handling bugs create risk of access control bypass
This Red Hat advisory covers CVE-2026-63385 in Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8 and Red Hat Enterprise Linux 9.
Key facts
- Vendor rating
- High, CVSS 7.7
- CISA KEV
- Not listed (catalogue checked )
- Affected
- < 2.1.13; < 2.2.2-alpha
- Fixed in
- 2.1.13, 2.2.2, libevent-0:2.1.13-1.el10_2 and 30 more below
- Source published
- Listed by VulniPulse
Compiled by VulniPulse from the linked sources. How records are collected and checked.
Affected products & platforms
Description
Libevent 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. A flaw was found in libevent.
The evhttp_decode_uri_internal function in http.c decodes percent-encoded %00 bytes into literal NUL characters without rejecting them, allowing an attacker to craft a URI such as /admin/secret%00.jpg where extension-based access checks see.jpg but the server processes /admin/secret, bypassing path-based access controls.
Additionally, evhttp_header_is_valid_value accepts obsolete HTTP header line folding (CRLF followed by SP/HT), which RFC 9112 states new implementations should reject, creating a header injection vector in proxy chains where the frontend rejects obs-fold but libevent accepts it.
Text from the source record.
- < 2.1.13
- < 2.2.2-alpha
Official advisory · high-confidence parse· fetched ·verify at source
How to fix CVE-2026-63385
Upgrade to a fixed release named by Red Hat:
- 2.1.13
- 2.2.2
- libevent-0:2.1.13-1.el10_2
- libevent-0:2.1.8-11.el8_10
- libevent-0:2.1.13-1.el9_8
- openshift/ose-rhel-coreos-9:4.22.9.8.202609291947-0
- cert-manager/jetstack-cert-manager-rhel9:1790223279
- cert-manager/cert-manager-istio-csr-rhel9:1790223719
- cert-manager/cert-manager-operator-rhel9:1790272426
- cert-manager/jetstack-cert-manager-acmesolver-rhel9:1790589998
- cert-manager/jetstack-cert-manager-rhel9:1790589912
- cert-manager/cert-manager-istio-csr-rhel9:1790589914
- cert-manager/cert-manager-operator-rhel9:1790589855
- libevent-main-2.1.13-0.1.hum1
- libevent-main-2.1.13-1.hum1
- rhui5/cds-kubernetes-rhel9:1790241897
- rhui5/cds-rhel9:1790241954
- rhui5/haproxy-rhel9:1790241900
- rhui5/installer-rhel9:1790241922
- rhui5/rhua-rhel9:1790242004
- RHSA-2026:67909
- RHSA-2026:67908
- RHSA-2026:67910
- RHSA-2026:74428
- RHSA-2026:72394
and 8 more in the Red Hat advisory.
Vendor guidance
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Support dates for the fixed release lines
- Red Hat Enterprise Linux 4: support ended
CVE-2026-63385 in other vendors' advisories
- Veeam: KB4825
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