CVE-2026-63385 Libevent: HTTP header handling bugs create risk of access control bypass.
Attackers can bypass access controls or inject headers in applications using Libevent due to URI decoding and header parsing flaws.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63385?
CVE-2026-63385 is a critical vulnerability in libevent, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-444
Which versions are affected by CVE-2026-63385?
Linux distribution packages (3)
libevent Red Hat:hummingbird:1 | All versions | 0:2.1.13-1.hum1 |
libevent-devel Red Hat:hummingbird:1 | All versions | 0:2.1.13-1.hum1 |
libevent-doc Red Hat:hummingbird:1 | All versions | 0:2.1.13-1.hum1 |
How do I fix CVE-2026-63385?
Apply the vendor's patch.
Is CVE-2026-63385 being exploited?
There is no known exploitation of CVE-2026-63385 in the wild and no public exploit code.
Sources
Also known as AZL-96897, AZL-96947, AZL-97539, AZL-97566, BELL-CVE-2026-63385, DEBIAN-CVE-2026-63385 and 5 more.