CVE-2026-63495
Libevent: Unbounded memory accumulation in WebSocket server via fragmented frames
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-400 CWE-770 |
| Vendor | libevent |
| Product | libevent |
| Published | Aug 20, 2026 |
| Last Updated | Aug 20, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
libevent / libevent
>= 2.2.0-alpha-dev, < 2.2.2-alpha