undici WebSocket client vulnerable to denial of service via fragment count bypass

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Summary

CVECVE-2026-12151
StatePUBLISHED
Assigneropenjs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-17 17:16:42 UTC
Updated2026-06-17 20:20:10 UTC
DescriptionImpact: The undici WebSocket client enforces maxPayloadSize on the cumulative byte count of fragments in a message but does not enforce a limit on the number of fragments. A malicious WebSocket server can stream many small or empty continuation frames that each pass per-frame and cumulative-size validation, collectively causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service. Affected applications are those using the undici WebSocket client (new WebSocket(...)) or the WebSocketStream API that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint. All releases starting at undici 6.17.0 are affected. Patches: Upgrade to undici >= 6.26.0, >= 7.28.0, or >= 8.5.0. Workarounds: No workaround is available. The fix must be applied through an upgrade.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ce714d77-add3-4f53-aff5-83d477b104bb

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

EPSS: 0.002840000 probability, percentile 0.199130000 (date 2026-06-22)

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
3.1ce714d77-add3-4f53-aff5-83d477b104bbSecondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNACVSS7.5HIGHCVSS: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 Undici Undici affected 6.26.0 semver Not specified
CNA Undici Undici unaffected 6.26.0 semver Not specified
CNA Undici Undici affected 7.0.0 7.28.0 semver Not specified
CNA Undici Undici unaffected 7.28.0 semver Not specified
CNA Undici Undici affected 8.0.0 8.5.0 semver Not specified
CNA Undici Undici unaffected 8.5.0 semver Not specified

References

ReferenceSourceLinkTags
cna.openjsf.org/security-advisories.html ce714d77-add3-4f53-aff5-83d477b104bb cna.openjsf.org
github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q ce714d77-add3-4f53-aff5-83d477b104bb github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: lpinca (en)

CNA: Nadav0077 (en)

CNA: UlisesGascon (en)

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