CVE-2026-63495CWE-400CWE-770denial-of-service

CVE-2026-63495

High · published August 20, 2026

CVSS v3.1
7.5
EPSS
1%
Percentile
48.5
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS v4.0
Not supplied
EPSS
0.00609 · 48.5th percentile
Weaknesses
CWE-400 · Uncontrolled Resource Consumption; CWE-770 · Allocation of Resources Without Limits or Throttling
Published
2026-08-20T22:16Z
References (4)
https://github.com/libevent/libevent/commit/291c4d1cd75695e898030ebd5c4ddf26c094077b · [email protected]https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha · [email protected]https://github.com/libevent/libevent/security/advisories/GHSA-qx89-wf2v-vgmx · [email protected]https://github.com/libevent/libevent/security/advisories/GHSA-qx89-wf2v-vgmx · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 20 AUG 17:49Z
    Libevent: Unbounded memory accumulation in WebSocket server via fragmented frames
    cvelistv5