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CVE-2026-71566 – Authentication Bypass / Unauthorized VM Control – FakeFish (openshift-metal3) up to

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Summary

CVE-2026-71566 is a critical missing-authentication vulnerability (CWE-306) in FakeFish, the Redfish-compatible BMC emulator maintained by the openshift-metal3 project used to manage KubeVirt-backed virtual "bare metal" hosts. When FakeFish is deployed against the KubeVirt backend, it silently ignores the credentials supplied in incoming requests and instead relies solely on a mounted KUBECONFIG file for cluster access, meaning any user who can reach the FakeFish endpoint can issue commands with no valid authentication at all. The issue carries a CVSS v3.1 base score of 9.3 (Critical) and can result in unauthorized power control and virtual media manipulation of victim VMs.

Technical details

  • Root cause: FakeFish’s credential-validation logic is designed for physical BMC hardware, where supplied credentials are passed through to vendor scripts that validate them against the actual hardware BMC. The KubeVirt backend, however, never validates the supplied credentials — it authenticates to the Kubernetes cluster using a mounted KUBECONFIG file regardless of what credentials (if any) are presented in the request.
  • Trigger conditions: Any FakeFish instance running the KubeVirt backend that is reachable over the network (including via routes configured per the documented deployment pattern) is exploitable without any prior authentication.
  • Attack vector: Network (AV:N), no privileges required (PR:N), no user interaction (UI:N) — an attacker only needs network access to the FakeFish Redfish API endpoint.
  • Impact: Any cluster user (or unauthenticated network client, depending on exposure) can manipulate virtual machines belonging to the FakeFish instance’s owner, including powering VMs on/off and mounting arbitrary/unauthorized virtual CD images — enabling denial of service and potential follow-on compromise via malicious virtual media. The CVSS vector reflects no confidentiality impact, low integrity impact, and high availability impact (C:N/I:L/A:H).

Affected software

  • Product: FakeFish (openshift-metal3/fakefish)
  • Vulnerable range: All git revisions from the initial commit through commit 28f9a6b
  • Fixed in: Commit 526550a (with the credential-mount enforcement implemented at 5889d2c)

Severity

  • CVSS v3.1 Base Score: 9.3 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:H

Mitigation and recommended actions

  • Immediate: Upgrade FakeFish to a version built from commit 526550a or later, and ensure the fix’s enforcement mechanism is active:
    • Direct/binary deployments must be started with the --validate-credentials flag.
    • Containerfile-based deployments must mount valid credentials at /tmp/fakefish-credentials; without this mount, the patched FakeFish will refuse to start, preventing insecure operation.
  • If immediate patching is not possible: Deploy an authentication proxy in front of FakeFish to enforce access control before requests reach the FakeFish service, and restrict network reachability of the FakeFish endpoint/route to trusted hosts only.
  • Review any exposed FakeFish routes for unnecessary external network exposure and audit VM power/media-mount activity for signs of unauthorized access during the exposure window.

References

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