Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-08-20T17:52:29 libevent: Libevent: Denial of Service via Null Pointer Dereference 4.7 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H CWE-476

Libevent is an event notification library. Prior to 2.2.2-alpha, libevent can dereference invalid list pointers in ws.c when evws_new_session enters its error path after evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails. evws_connection_free sees a non-null http_server and unconditionally calls TAILQ_REMOVE even though the session was never inserted into http_server->ws_sessions. A local caller able to induce this allocation or locking failure can crash the process. This issue is fixed in version 2.2.2-alpha.

A flaw was found in Libevent, an event notification library. This vulnerability allows a local attacker to trigger a null pointer dereference during specific error handling within the `evws_new_session` function. By inducing an allocation or locking failure, an attacker can cause the application to crash, leading to a denial of service.

Moderate impact. A null pointer dereference in Libevent's websocket handling can be triggered by a local attacker. This flaw allows a local caller to induce specific allocation or locking failures during websocket session creation, leading to a denial of service. Exploitation is limited to applications utilizing Libevent's websocket functionality and exposed to untrusted local input. The vulnerable code module has only ever shipped as part of the 2.2.x development/alpha line, culminating in the 2.2.2-alpha release that fixes this issue. It was never backported into the 2.1.x stable series. Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Red Hat Enterprise Linux 10 Fix deferred libevent Red Hat Enterprise Linux 6 Out of support scope libevent Red Hat Enterprise Linux 6 Out of support scope libevent2 Red Hat Enterprise Linux 7 Fix deferred libevent Red Hat Enterprise Linux 8 Fix deferred libevent Red Hat Enterprise Linux 9 Not affected libevent Red Hat Hardened Images Not affected libevent Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-63380 https://nvd.nist.gov/vuln/detail/CVE-2026-63380 https://github.com/libevent/libevent/commit/825c18bd99f556b59d61200523237f264d5cc734 https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha https://github.com/libevent/libevent/security/advisories/GHSA-3rpf-frgx-xq34