High [CVE-2026-63495] Remote denial of service via unbounded memory accumulation in WebSocket server
This high-severity Red Hat Linux advisory covers CVE-2026-63495 affecting Red Hat Hardened Images, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6.
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Summary
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.
A flaw was found in Libevent. Due to a lack of a total message-size limit, these fragmented frames accumulate in memory without bound, leading to memory exhaustion and a denial of service (DoS) for the process or host.
Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-770.
Affected Red Hat products: Red Hat Hardened Images; Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat OpenShift Container Platform 4. Red Hat fixing advisory: RHSA-2026:41176.
Affected products named by the advisory: Red Hat package: libevent2.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
- 2.2.2
- libevent-main-2.1.12-19.hum1
- RHSA-2026:41176
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation
Upgrade to a fixed release: 2.2.2, libevent-main-2.1.12-19.hum1, RHSA-2026:41176. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
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