Libevent: Unbounded memory accumulation in WebSocket server via fragmented frames

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63495
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-20 18:16:37 UTC
Updated2026-08-20 20:17:45 UTC
DescriptionLibevent 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-400 | CWE-770 | CWE-400 CWE-400: Uncontrolled Resource Consumption | CWE-770 CWE-770: Allocation of Resources Without Limits or Throttling

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Libevent Libevent affected >= 2.2.0-alpha-dev, < 2.2.2-alpha Not specified

References

ReferenceSourceLinkTags
github.com/libevent/libevent/commit/291c4d1cd75695e898030ebd5c4ddf26c094... [email protected] github.com
github.com/libevent/libevent/security/advisories/GHSA-qx89-wf2v-vgmx 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/libevent/libevent/releases/tag/release-2.2.2-alpha [email protected] github.com
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