# CVE-2026-63380: Libevent null pointer dereference in evws_new_session error path

Source: https://junglewise.ai/threats/cve-2026-63380-libevent-null-pointer-dereference-in-evws-new-session-error-path  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-20. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-63380 · Severity: info · CVSS 0 · Published 2026-08-20

Libevent is an event notification library used by many networked applications to handle asynchronous event processing. A flaw in the WebSocket session creation code can cause the library to crash when memory allocation or locking operations fail, potentially disrupting services that depend on it. A local attacker able to trigger these specific failure conditions could cause a denial of service.

Technologies: [Libevent](https://junglewise.ai/threats/technologies/libevent). Vendors: [Libevent](https://junglewise.ai/threats/vendors/libevent).

## Quick answers

**Is CVE-2026-63380 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63380 being exploited in the wild.

**How severe is CVE-2026-63380?** Informational severity, with a CVSS score of 0, published 20 August 2026.

**Which products and versions are affected?** Libevent prior to 2.2.2-alpha.

**Is there a fix for CVE-2026-63380?** A patch was published on 2026-07-01: Fixed in version 2.2.2-alpha Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-63380 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-63380?** Check whether you run Libevent at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a null pointer dereference in the error path of the evws_new_session() function in ws.c. The root cause is a logic error where evws_connection_free() calls TAILQ_REMOVE on a websocket session that was never inserted into the http_server->ws_sessions list, because the failure occurred after evhttp_start_ws_() succeeded but before bufferevent_enable_locking_() completed. This causes the function to dereference invalid list pointers and trigger a segmentation fault. The attack requires local access and the ability to induce specific memory allocation or locking failures. The issue is fixed in version 2.2.2-alpha and later.

## Affected products

- Libevent Libevent prior to 2.2.2-alpha

## Timeline

- 2026-08-20: disclosed
- 2026-07-01: patched: Fixed in version 2.2.2-alpha

## References

- [https://github.com/libevent/libevent/commit/825c18bd99f556b59d61200523237f264d5cc734](https://github.com/libevent/libevent/commit/825c18bd99f556b59d61200523237f264d5cc734)
- [https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha](https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha)

## Related threats

- [Libevent WebSocket unbounded memory accumulation via frame fragmentation](https://junglewise.ai/threats/cve-2026-63495-libevent-websocket-unbounded-memory-accumulation-via-frame)
- [Libevent heap out-of-bounds write in bufferevent_sock](https://junglewise.ai/threats/cve-2026-63388-libevent-heap-out-of-bounds-write-in-bufferevent-sock)
- [Libevent off-by-one stack buffer overflow in DNS response parsing](https://junglewise.ai/threats/cve-2026-63387-libevent-off-by-one-stack-buffer-overflow-in-dns-response-parsing)
- [Libevent integer overflow in evtag_unmarshal_header](https://junglewise.ai/threats/cve-2026-63384-libevent-integer-overflow-in-evtag-unmarshal-header)
- [Libevent out-of-bounds read in event_tagging](https://junglewise.ai/threats/cve-2026-63383-libevent-out-of-bounds-read-in-event-tagging)