CVE-2026-63385

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. This could lead to access control bypass, header injection, or request smuggling.

Red Hat Enterprise Linux, OpenShift (RHCOS), RHIVOS, and community products (Fedora, Hummingbird) ship affected versions of libevent.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

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.