CVE-2026-63381 Libevent: Dangling Pointer in `evbuffer_add_buffer_reference`
A use-after-free in Libevent allows attackers to cause memory corruption or crashes via crafted buffer states, requiring an upgrade to patched versions.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63381?
CVE-2026-63381 is a medium-severity use after free vulnerability in libevent, published on 20 Aug 2026. It can only be exploited from the same machine or local network, 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 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.
Weakness: CWE-908
Which versions are affected by CVE-2026-63381?
How do I fix CVE-2026-63381?
Upgrade to a fixed version.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-63381 being exploited?
There is no known exploitation of CVE-2026-63381 in the wild and no public exploit code.
Sources
Also known as AZL-96915, AZL-96953, AZL-97527, AZL-97545, BELL-CVE-2026-63381, DEBIAN-CVE-2026-63381 and 4 more.