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_… (CVE-2026-63380)
Description
Libevent versions prior to 2.2.2-alpha contain a vulnerability in ws.c where invalid list pointers can be dereferenced during error handling in evws_new_session. This occurs when evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails, leading to a call to TAILQ_REMOVE on a session not inserted into the session list. This can cause a process crash. The issue is fixed in version 2.2.2-alpha.
CVSS v4.0
Affected software
pkg:deb/ubuntu/libevent?arch=source&distro=trustypkg:deb/ubuntu/libevent?arch=source&distro=xenialpkg:deb/ubuntu/libevent?arch=source&distro=bionicpkg:deb/ubuntu/libevent?arch=source&distro=focalpkg:deb/ubuntu/libevent?arch=source&distro=jammypkg:deb/ubuntu/libevent?arch=source&distro=noblepkg:deb/ubuntu/libevent?arch=source&distro=resolutepkg:deb/ubuntu/libevent?arch=source&distro=esm-infra-legacy/trustypkg:deb/ubuntu/libevent?arch=source&distro=esm-infra-legacy/xenialpkg:deb/ubuntu/libevent?arch=source&distro=esm-infra/bionicpkg:deb/ubuntu/libevent?arch=source&distro=esm-infra/focalRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Libevent is an event notification library. In versions before 2.2.2-alpha, a flaw exists in the WebSocket session handling code (ws.c). Specifically, if evws_new_session enters its error path after evhttp_start_ws_ succeeds but bufferevent_enable_locking_ fails, evws_connection_free unconditionally calls TAILQ_REMOVE on a non-null http_server pointer. Since the session was never inserted into http_server->ws_sessions, this leads to dereferencing invalid list pointers. A local attacker able to trigger this allocation or locking failure can cause the process to crash. The vulnerability is resolved in libevent version 2.2.2-alpha.
Potential Impact
A local attacker with the ability to induce allocation or locking failures in the affected libevent versions can cause the process to crash due to invalid pointer dereference. This results in denial of service but does not indicate code execution or data corruption from the provided data.
Mitigation Recommendations
This vulnerability is fixed in libevent version 2.2.2-alpha. Users should upgrade to version 2.2.2-alpha or later to remediate this issue. No other mitigation or workaround is indicated.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-63380
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:14.04:LTS","Ubuntu:16.04:LTS","Ubuntu:18.04:LTS","Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:26.04:LTS"]
- Cvss Version
- 4.0
Threat ID: 6a8c4c54acd9273b499be7dc
Added to database: 08/24/2026, 13:51:16 UTC
Last enriched: 09/29/2026, 05:10:49 UTC
Last updated: 10/06/2026, 18:48:23 UTC
Views: 37
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