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CVE-2026-44939 – YAML Injection / Command Injection Leading to RCE and Container Escape – SUSE Ra…

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Summary

CVE-2026-44939 is a critical command injection vulnerability in SUSE Rancher Manager affecting the cluster import endpoint /v3/import/{token}_{clusterId}.yaml. The flaw stems from the authImage query parameter being rendered without sanitization into a generated Kubernetes manifest template, allowing remote attackers to inject arbitrary YAML and execute malicious containers — effectively achieving remote code execution and container escape. The vulnerability carries a CVSS 4.0 score of 9.4 (Critical) and is exploitable over the network with no privileges required.

Technical details

  • Root cause: The authImage query parameter accepted by the cluster import endpoint is inserted directly into a Kubernetes manifest (YAML) template without input validation. Because YAML treats newlines as structural delimiters, an attacker can supply URL-encoded newline characters (%0A) to break out of the intended image field and inject arbitrary YAML keys and values into the rendered manifest.
  • Trigger conditions: An attacker must be able to send a crafted HTTP request to /v3/import/{token}_{clusterId}.yaml with a malicious authImage value. A cluster registration token is required to reach the endpoint; however, such tokens can be exposed through documentation, screenshots, or other channels.
  • Attack vector: Network-reachable, no authentication or privileges required (PR:N). The Rancher API (/v3/ family) is commonly exposed directly on the internet for multi-cluster management.
  • Impact: Successful exploitation enables full downstream cluster compromise, including: arbitrary code execution on control-plane nodes with elevated privileges; access to sensitive cluster secrets via the cattle service account; persistent attacker presence through deployed DaemonSets; and complete disruption of cluster operations.

Affected software

  • Rancher Manager 2.14.0 to < 2.14.2
  • Rancher Manager 2.13.0 to < 2.13.6
  • Rancher Manager 2.12.0 to < 2.12.10
  • Rancher Manager 2.11.0 to < 2.11.14
  • Rancher Manager 2.10.0 to < 2.10.12

Severity

CVSS v3.1 Base Score: 9.6 (Critical)
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

CVSS v4.0 Base Score: 9.4 (Critical)
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Mitigation and recommended actions

  • Immediate action — upgrade to a patched release:
    • Rancher 2.14.2 or later
    • Rancher 2.13.6 or later
    • Rancher 2.12.10 or later
    • Rancher 2.11.14 or later
    • Rancher 2.10.12 or later
  • The fix validates the authImage parameter to permit only valid OCI image reference characters, rejecting any input containing newlines, whitespace, or other characters capable of disrupting YAML syntax.
  • If immediate patching is not feasible, restrict network-level access to the Rancher API (/v3/import/ endpoint) to trusted IP ranges only, and ensure cluster registration tokens are not exposed publicly.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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