Expired pointer dereference in libevent - CVE-2026-63381

Vulnerability identifier: #VU136949

CSH Severity: Low

CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-63381

CWE-ID: CWE-825

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to disclose sensitive information.

The vulnerability exists due to a dangling pointer in evbuffer_add_buffer_reference when handling a buffer state where out_total_len == 0. A remote attacker can trigger a specific sequence of buffer operations to disclose sensitive information.

The issue was found by fuzzing, and exploitation appears to require a specific sequence of buffer operations.

libevent
Debian Linux
IBM i
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
Ubuntu
openEuler
Fedora
libevent (Ubuntu package)
libevent
libevent-debuginfo
libevent-debugsource
libevent-devel
libevent (Debian package)
libevent (Red Hat package)

Install security update from vendor's website.

libevent - update to 2.1.13
libevent (Ubuntu package) - addressed in versions 2.0.21-stable-2ubuntu0.16.04.1+esm1, 2.0.21-stable-1ubuntu1.14.04.2+esm1, 2.1.8-stable-4ubuntu0.1~esm1, 2.1.11-stable-1ubuntu0.1~esm1, 2.1.12-stable-1ubuntu0.1, 2.1.12-stable-10ubuntu0.1, 2.1.12-stable-9ubuntu2.1
libevent - update to 2.1.12-17
libevent-debuginfo - update to 2.1.12-17
libevent-debugsource - update to 2.1.12-17
libevent-devel - update to 2.1.12-17
libevent (Debian package) - update to 2.1.13-stable-1~deb13u1
libevent (Red Hat package) - update to 2.1.13-1.el10_2
libevent - addressed in versions 2.1.13-1.fc43, 2.1.13-1.fc44, 2.1.13-1.fc45

• https://github.com/libevent/libevent/security/advisories/GHSA-c2pj-cg4r-88c8
• https://github.com/libevent/libevent/blob/a994a52d5373d6284b27576efa617aff2baa7bd3/buffer.c#L1037-L1078

• Multiple vulnerabilities in libevent
• openEuler update for libevent
• Ubuntu update for libevent
• Fedora 45 update for libevent
• Fedora 44 update for libevent
• Fedora 43 update for libevent
• Debian update for libevent
• Multiple vulnerabilities in IBM i
• Red Hat Enterprise Linux 10 update for libevent