CVE-2026-63381: Libevent

Medium severity, CVSS 5.8. EPSS: 0.2% chance of exploitation in the next 30 days.

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 products

• Libevent Libevent: from 2.2.0-alpha, before 2.2.2-alpha (fixed in 2.2.2-alpha); before 2.1.13 (fixed in 2.1.13)

Published 2026-08-20. Last modified 2026-09-09.