Vulnerability · Published Aug 20, 2026 · Assigned by GitHub_M
CVE-2026-63380Libevent: Null Pointer Dereference in `evws_new_session`
Medium 5.7
In plain English
A medium-severity use-after-free in libevent from libevent. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 3% of all known vulnerabilities).
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu:22.04:LTS | libevent | no fix listed | UBUNTU-CVE-2026-63380 |
| Ubuntu:24.04:LTS | libevent | no fix listed | UBUNTU-CVE-2026-63380 |
| Ubuntu:26.04:LTS | libevent | no fix listed | UBUNTU-CVE-2026-63380 |
| Ubuntu:26.10 | libevent | no fix listed | UBUNTU-CVE-2026-63380 |
Affected products (as reported)
Weakness: CWE-416, CWE-476 · Vector: CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N