Resource exhaustion in Libevent
CVE-2026-63495
Libevent is an event notification library. From 2.2.0-alpha-dev until 2.2.2-alpha, the libevent WebSocket server in ws.c accumulates fragmented frames in evws->incomplete_frames without enforcing a total message-size limit. An unauthenticated remote client can repeatedly send fragmented WebSocket frames below WS_MAX_RECV_FRAME_SZ with FIN=0, causing the evbuffer to grow without bound until the process or host exhausts memory. This issue is fixed in version 2.2.2-alpha.
Vulnerability class: DoS (Denial of Service)
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
Affected products
- Libevent — versions >= 2.2.0-alpha-dev, < 2.2.2-alpha
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-63495?
- CVE-2026-63495 is a high-severity vulnerability in Libevent, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-08-20.
- How severe is CVE-2026-63495?
- High severity. CVSS v3 base score is 7.5 out of 10.