# CVE-2026-63385: Libevent HTTP parsing weaknesses in header validation and URI decoding

Source: https://junglewise.ai/threats/cve-2026-63385-libevent-http-parsing-weaknesses-in-header-validation-and-uri  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-20. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-63385 · Severity: info · Published 2026-08-20

Libevent is a widely-used event notification library that handles network communication for many applications. Two HTTP parsing flaws allow attackers to bypass security checks: one permits NUL byte injection in URI paths causing string truncation, and another accepts obsolete header line folding that enables header injection. These weaknesses could allow an attacker to access restricted resources, inject malicious headers, or bypass access controls on systems using affected versions.

## Quick answers

**Is CVE-2026-63385 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63385 being exploited in the wild.

**How severe is CVE-2026-63385?** Informational severity, published 20 August 2026.

**Which products and versions are affected?** Libevent Project Libevent prior to 2.1.13 and 2.2.2-alpha.

**Is there a fix for CVE-2026-63385?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-63385 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-63385?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

Libevent contains two distinct HTTP parsing vulnerabilities in http.c. The first flaw exists in evhttp_decode_uri_internal, which decodes percent-encoded %00 bytes into literal NUL characters; when these NUL bytes are processed by downstream C string operations, they cause path truncation, allowing an attacker to bypass URI validation checks that operate on a different representation. The second vulnerability occurs in evhttp_header_is_valid_value, which incorrectly accepts obsolete RFC 5322 line folding (carriage return and line feed characters within header values). This permits header injection attacks that can cause proxy chains and libevent to interpret headers differently, potentially enabling access control bypass. The CRLF header issue is fixed in versions 2.1.13 and 2.2.2-alpha, but the NUL-truncation condition in URI decoding remains inadequately addressed in the reviewed patches. Both issues are network-reachable and require no authentication or user interaction.

## Affected products

- Libevent Project Libevent prior to 2.1.13 and 2.2.2-alpha

## Timeline

- 2026-08-20: disclosed

## References

- [https://github.com/libevent/libevent/commit/758be0c0f69c1934ef9a84ab39e9f9e5fde2e6d0](https://github.com/libevent/libevent/commit/758be0c0f69c1934ef9a84ab39e9f9e5fde2e6d0)
- [https://github.com/libevent/libevent/commit/9170dd35e64714613e8d13b290587cfc28e258e2](https://github.com/libevent/libevent/commit/9170dd35e64714613e8d13b290587cfc28e258e2)