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libevent CVE-2026-63495

| EUVDEUVD-2026-63503 HIGH
Uncontrolled Resource Consumption (CWE-400)
2026-08-20 GitHub_M
Denial Of Service Libevent Suse
7.5
CVSS 3.1 · Vendor: GitHub_M
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Severity by source

Vendor (GitHub_M) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
vuln.today AI
7.5 HIGH

Network-reachable endpoint requires no authentication or complexity; impact is pure memory exhaustion causing process crash with no confidentiality or integrity effect.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
HIGH
qualitative

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

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

Lifecycle Timeline

4
Source Code Evidence Fetched
Aug 20, 2026 - 18:24 vuln.today
Analysis Generated
Aug 20, 2026 - 18:24 vuln.today
Patch available
Aug 20, 2026 - 18:03 EUVD
CVE Published
Aug 20, 2026 - 17:49 cve.org
HIGH 7.5

DescriptionCVE.org

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.

AnalysisAI

Memory exhaustion in libevent's WebSocket server (ws.c) allows unauthenticated remote clients to crash affected processes by sending an unbounded stream of fragmented WebSocket frames. Affected versions span 2.2.0-alpha-dev through pre-fix 2.2.2-alpha; the evws WebSocket API enforces WS_MAX_RECV_FRAME_SZ per individual frame but applies no cap to the total accumulated message size in evws->incomplete_frames, enabling heap growth without limit. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation The vulnerable code path is active whenever an application uses libevent's evws WebSocket server API from versions 2.2.0-alpha-dev to 2.2.2-alpha (pre-fix). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (score 7.5) accurately characterizes the attack surface: no authentication, no complexity, no user interaction, fully network-reachable. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade to libevent 2.2.2-alpha, which enforces a total accumulated message-size limit during fragmented frame reassembly and closes the WebSocket connection with close code 1009 (message too large) when that limit is exceeded; the release is available at https://github.com/libevent/libevent/releases/tag/release-2.2.2-alpha and the implementing commit is 291c4d1cd75695e898030ebd5c4ddf26c094077b. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, inventory systems running libevent WebSocket services and identify those on affected versions 2.2.0-alpha through 2.2.2-alpha. …

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 12 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise Micro 5.3 Affected
SUSE Linux Enterprise Micro 5.4 Affected

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CVE-2026-63495 vulnerability details – vuln.today
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