CVE-2026-9675 (GCVE-0-2026-9675)

Vulnerability from cvelistv5 – Published: 2026-06-17 16:20 – Updated: 2026-06-17 17:29
VLAI
Title
undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
Summary
Impact: The undici WebSocket client enforces maxPayloadSize per-frame but does not enforce the cumulative size of fragmented uncompressed messages. A malicious WebSocket server can stream many small fragments that each pass per-frame validation but collectively exceed the configured limit, 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(...)) that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint. This is a regression specific to undici 8.1.0. The 6.25.0 line shipped the equivalent cumulative check from the start and is unaffected. The 7.x line never had the maxPayloadSize feature and is also unaffected. Patches: Upgrade to undici >= 8.5.0. Workarounds: No workaround is available. The fix must be applied through an upgrade.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-17 17:29 UTC
CWE
  • CWE-400 - Uncontrolled Resource Consumption
  • CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
openjs CNA under the redhat root
CNA scorecard C 65/100 over 121 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
undici undici Affected: 8.0.0 , < 8.5.0 (semver)
Unaffected: 8.5.0 (semver)
guessed Create a notification for this product.
Credits
mauriceng98 Str1ckl4nd mcollina UlisesGascon lzhou1110 Zyy0530
Show details on NVD website
To clipboard 

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