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CVE-2026-100558 – Denial of Service (Resource Exhaustion) – OpenClaw before 2026.8.1

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Summary

CVE-2026-100558 is a resource exhaustion vulnerability (CWE-400) in the Gateway listener of OpenClaw, an npm-distributed product. Unauthenticated remote attackers can send WebSocket upgrade requests that lack matching connection semantics, causing the listener to hold open response sockets and associated request state without consuming the WebSocket pre-authentication connection budget. Repeated exploitation exhausts listener resources and causes denial of service; the flaw carries a CVSS v4.0 base score of 8.7 (High).

Technical details

  • Root cause: The Gateway listener routes HTTP requests that present a WebSocket upgrade header but lack proper connection semantics to a standard handler, which fails to properly terminate the response, leaving the socket and request state open.
  • Trigger conditions: An attacker sends malformed WebSocket upgrade requests to the Gateway listener; because these requests do not match expected connection semantics, they bypass the normal WebSocket pre-authentication connection budget that would otherwise limit resource use.
  • Attack vector: Network-based, no authentication or user interaction required, low attack complexity.
  • Impact: Exhaustion of listener resources leading to denial of service (availability impact only — no confidentiality or integrity impact).

Affected software

  • OpenClaw (npm package openclaw) — all versions prior to 2026.8.1
  • Fixed in version 2026.8.1 and later

Severity

  • CVSS v3.1: 7.5 (High) — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  • CVSS v4.0: 8.7 (High) — CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Mitigation and recommended actions

  • Immediate: Upgrade OpenClaw to version 2026.8.1 or later, which fixes the Gateway listener’s handling of malformed upgrade requests.
  • If unable to patch immediately:
    • Restrict access to the Gateway listener to loopback-only where possible.
    • Place the Gateway behind a reverse proxy that validates WebSocket upgrade requests and enforces its own connection limits before traffic reaches OpenClaw.

References

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