High · CVSS 7.5CVE-2026-63495

Libevent: Unbounded memory accumulation in WebSocket server via fragmented framesCVE-2026-63495

Answer in brief

CVE-2026-63495 records a High severity (CVSS 7.5) vulnerability in Libevent: Unbounded memory accumulation in WebSocket server via fragmented frames. The current sources do not mark it as known exploited. The current feed maps libevent/libevent (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 20, 2026Updated Sep 9, 2026Source checked Oct 4, 2026First seen by HOL Aug 20, 2026Material review Sep 9, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps libevent/libevent (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
libevent/libeventgeneric	>=2.2.0-alpha-dev <2.2.2-alpha	2.2.2-alpha

Recommended response

Check inventory. Check lockfiles and deployed manifests for libevent/libevent.
Review the reported fix. Update libevent/libevent to 2.2.2-alpha if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 20, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 9, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 20, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.