Riskcovery

CVE-2026-12151

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

State
Published
Severity
7.5 High
Published
Jun 17, 2026
Updated
Sep 11, 2026
Reserved
Jun 12, 2026

Read the record on cve.org

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.

Scores

CVSSScoreVectorSource
3.17.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hopenjs
3.17.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hredhat-SADP

Weaknesses

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

Affected Products

ProductVersions
undiciundici
  • before 6.26.0Affected
  • 6.26.0Not affected
  • 7.0.0 to before 7.28.0Affected
  • 7.28.0Not affected
  • 8.0.0 to before 8.5.0Affected
  • 8.5.0Not affected

References

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