Impact: 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.
References
Link Providers
https://access.redhat.com/errata/RHSA-2026:34342 cve-icon
https://access.redhat.com/errata/RHSA-2026:35841 cve-icon
https://access.redhat.com/errata/RHSA-2026:35842 cve-icon
https://access.redhat.com/errata/RHSA-2026:35891 cve-icon
https://access.redhat.com/errata/RHSA-2026:35892 cve-icon
https://access.redhat.com/errata/RHSA-2026:36621 cve-icon
https://access.redhat.com/errata/RHSA-2026:36754 cve-icon
https://access.redhat.com/errata/RHSA-2026:36820 cve-icon
https://access.redhat.com/errata/RHSA-2026:38009 cve-icon
https://access.redhat.com/errata/RHSA-2026:38236 cve-icon
https://access.redhat.com/errata/RHSA-2026:39246 cve-icon
https://access.redhat.com/errata/RHSA-2026:39868 cve-icon
https://access.redhat.com/errata/RHSA-2026:41929 cve-icon
https://access.redhat.com/errata/RHSA-2026:41947 cve-icon
https://access.redhat.com/errata/RHSA-2026:47728 cve-icon
https://access.redhat.com/errata/RHSA-2026:48124 cve-icon
https://access.redhat.com/errata/RHSA-2026:48151 cve-icon
https://access.redhat.com/errata/RHSA-2026:52399 cve-icon
https://access.redhat.com/errata/RHSA-2026:56366 cve-icon
https://access.redhat.com/errata/RHSA-2026:56431 cve-icon
https://access.redhat.com/errata/RHSA-2026:57013 cve-icon
https://access.redhat.com/errata/RHSA-2026:60520 cve-icon
https://access.redhat.com/errata/RHSA-2026:62260 cve-icon
https://access.redhat.com/errata/RHSA-2026:65126 cve-icon
https://access.redhat.com/security/cve/CVE-2026-12151 cve-icon
https://bugzilla.redhat.com/show_bug.cgi?id=2489980 cve-icon
https://cna.openjsf.org/security-advisories.html cve-icon cve-icon cve-icon
https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-12151 cve-icon
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12151.json cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-12151 cve-icon
History

Wed, 09 Sep 2026 13:30:00 +0000

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Wed, 02 Sep 2026 13:30:00 +0000

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Fri, 28 Aug 2026 16:30:00 +0000

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Wed, 19 Aug 2026 12:30:00 +0000


Thu, 18 Jun 2026 19:15:00 +0000

Type Values Removed Values Added
First Time appeared Undici
Undici undici
Vendors & Products Undici
Undici undici

Thu, 18 Jun 2026 16:45:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Important


Thu, 18 Jun 2026 04:45:00 +0000

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Description Impact: 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.
Title undici WebSocket client vulnerable to denial of service via fragment count bypass
Weaknesses CWE-400
CWE-770
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


cve-icon MITRE

Status: PUBLISHED

Assigner: openjs

Published: 2026-06-17T16:05:38.785Z

Updated: 2026-09-09T12:05:07.605Z

Reserved: 2026-06-12T18:14:04.454Z

Link: CVE-2026-12151

cve-icon Vulnrichment

Updated: 2026-09-09T12:05:07.605Z

cve-icon NVD

Status : Modified

Published: 2026-06-17T17:16:42.370

Modified: 2026-09-09T13:18:35.397

Link: CVE-2026-12151

cve-icon Redhat

Severity : Important

Publid Date: 2026-06-17T16:05:38Z

Links: CVE-2026-12151 - Bugzilla