CVE-2026-63380
MEDIUMDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v4 Vector
Exploitability
Impact
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Exploit Intelligence
Low risk: more likely to be exploited than 2% of all known CVEs.
References
Related Vulnerabilities
Other CWE-416 (Use After Free) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2019-0708 | Critical | 9.8 | 100% | KEV + Ransom | - |
| CVE-2021-31166 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2015-5119 | Critical | 9.8 | 99% | KEV | - |
| CVE-2010-3962 | High | 8.1 | 97% | KEV | - |
| CVE-2015-0313 | Critical | 9.8 | 96% | KEV | Fix |
| CVE-2021-34833 | High | 7.8 | 96% | - | - |
Common questions
How do I fix CVE-2026-63380?
No published fix for CVE-2026-63380 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-63380 being actively exploited?
Not that we know of. CVE-2026-63380 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.11% is the estimated probability that it will be exploited in the next 30 days. That is higher than 2% of all scored CVEs.
How severe is CVE-2026-63380?
CVE-2026-63380 has a CVSS v4 base score of 5.7, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
Embed a live status badge for CVE-2026-63380
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-20.