CVE-2026-63381
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.
CSIRTS triage
- What
- Dangling pointer in evbuffer_add_buffer_reference() causes use-after-free conditions.
- Who is affected
- Applications using Libevent's evbuffer API for buffer management.
- Urgency
- High; memory corruption can lead to crashes or code execution; patch immediately upon release.
- Action
- Update Libevent to a version containing the dangling pointer fix.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all EPSS-scored CVEs.
Advisory coverage (2)
- unknownCVE-2026-63381: Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent has a use…nvd · 2026-08-20
- unknownCVE-2026-63381: Libevent: Dangling Pointer in `evbuffer_add_buffer_reference`msrc · 2026-08-11
External references
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[](https://www.csirts.com/cve/CVE-2026-63381)