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Vulnerability · Published Aug 20, 2026 · Assigned by GitHub_M

CVE-2026-63381Libevent: Dangling Pointer in `evbuffer_add_buffer_reference`

Medium 5.8

In plain English

A medium-severity security flaw in libevent from libevent. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 5% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)5.8Medium
Exploit odds (30 days)0.2%top 94.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has a use-after-free in buffer.c when evbuffer_add_buffer_reference processes an output buffer whose out_total_len is zero. evbuffer_free_all_chains frees the initial empty chain without resetting outbuf->first, outbuf->last, or outbuf->last_with_datap, and APPEND_CHAIN_MULTICAST subsequently dereferences the dangling chain pointer. A caller that can drive this buffer state can cause memory corruption or a process crash. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10libevent2.1.13-1.el10_2ALSA-2026:67909
AlmaLinux:9libevent2.1.13-1.el9_8ALSA-2026:67910
AlmaLinux:10libevent-devel2.1.13-1.el10_2ALSA-2026:67909
AlmaLinux:9libevent-devel2.1.13-1.el9_8ALSA-2026:67910
AlmaLinux:10libevent-doc2.1.13-1.el10_2ALSA-2026:67909
AlmaLinux:9libevent-doc2.1.13-1.el9_8ALSA-2026:67910
Debian:12libevent2.1.12-stable-8+deb12u1DEBIAN-CVE-2026-63381
Debian:13libevent2.1.13-stable-1~deb13u1DEBIAN-CVE-2026-63381
Debian:14libevent2.1.13-stable-1DEBIAN-CVE-2026-63381
Rocky Linux:10libevent0:2.1.13-1.el10_2RLSA-2026:67909
Rocky Linux:9libevent0:2.1.13-1.el9_8RLSA-2026:67910
Ubuntu:22.04:LTSlibevent2.1.12-stable-1ubuntu0.1UBUNTU-CVE-2026-63381
Ubuntu:22.04:LTSlibevent2.1.12-stable-1ubuntu0.1USN-8710-1
Ubuntu:24.04:LTSlibevent2.1.12-stable-9ubuntu2.1UBUNTU-CVE-2026-63381
Ubuntu:24.04:LTSlibevent2.1.12-stable-9ubuntu2.1USN-8710-1
Ubuntu:26.04:LTSlibevent2.1.12-stable-10ubuntu0.1USN-8710-1
Ubuntu:26.04:LTSlibevent2.1.12-stable-10ubuntu0.1UBUNTU-CVE-2026-63381

Affected products (as reported)

VendorProductVersions
libevent libevent >= 2.2.0-alpha, < 2.2.2-alpha< 2.1.13

Weakness: CWE-908 · Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N

References