CVE-2026-44939: Command injection through unsanitized YAML parameter in Rancher

Synopsis

A command injection vulnerability in Rancher Manager allows an unauthenticated remote attacker to exploit the cluster import endpoint (/v3/import/{token}_{clusterId}.yaml) by supplying unsanitized YAML parameters. The attacker must trigger a victim to interact with a crafted request, but no credentials are required. Successful exploitation enables container breakout and arbitrary command execution on the host, with full compromise of both the affected system and connected systems. Patched-image rebuilds at versions 2.10.12, 2.11.14, 2.12.10, 2.13.6, and 2.14.2 are available on HarborGuard for environments running an affected version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The vulnerable import endpoint is exposed over the network, so the attacker must be able to reach the Rancher Manager service via HTTP/HTTPS.

• AuthenticationNot required

  The import endpoint accepts requests without any credential or session token, so no account is needed to send a malicious payload.

• Victim interactionRequired

  Exploitation requires a victim (such as a cluster operator) to interact with or trigger processing of the attacker-supplied YAML, introducing a social-engineering step.

• Attack complexityDetail

  Attack complexity is low; the exploit is reliable and requires no race conditions, special memory layout, or environmental prerequisites beyond reaching the endpoint.

Blast Radius

• Attacker executes arbitrary commands inside the Rancher container and breaks out to the underlying host.
• Full read access to secrets, credentials, and configuration stored in the Rancher environment, including kubeconfig files and cluster tokens.
• Attacker can write to or modify cluster state, deploy malicious containers, and alter workloads across managed clusters.
• Connected downstream clusters inherit the compromise because Rancher's management plane can propagate attacker-controlled configurations to them.