CVE-2026-12151

Summary

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.

Affected Software

Weaknesses

• CWE-400: CWE-400: Uncontrolled Resource Consumption
• CWE-770: CWE-770: Allocation of Resources Without Limits or Throttling

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: yes
  • Technical Impact: partial

undici: undici: Denial of Service due to unbounded memory growth via WebSocket frames

Additional References

• https://access.redhat.com/security/cve/CVE-2026-12151
• https://bugzilla.redhat.com/show_bug.cgi?id=2489980
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12151.json
• https://access.redhat.com/errata/RHSA-2026:34342

References

• https://github.com/nodejs/undici/security/advisories/GHSA-vxpw-j846-p89q
• https://cna.openjsf.org/security-advisories.html

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