Fleet has PSS Bypass through addLabelsFromOptions in Fleet Agent

Overview

Impact

A vulnerability has been identified in Fleet's agent-side deployer, which did not filter security-sensitive keys from namespaceLabels in fleet.yaml (or BundleDeployment.spec.options.namespaceLabels) when applying them to the target namespace.

An attacker with git push access to a Fleet-monitored repository could overwrite Pod Security Standards (PSS) enforcement labels on a target namespace. This allows the attacker to weaken admission controls and deploy workloads that PSS policies would otherwise block.

Important: The final impact on confidentiality, integrity, and availability depends on the specific permissions of the leaked credentials.

Fleet team recommends you:

1. Review your system for potentially leaked credentials.
2. Replace any credentials that may be compromised.

Please consult the associated MITRE ATT&CK - Technique - Disable or Modify Tools for further information about this category of attack.

Patches

To fix this issue, upgrade to a patched version. The updated Fleet deployer filters out labels with the pod-security.kubernetes.io/ prefix when applying namespaceLabels to a namespace. This change preserves the PSS labels set by cluster administrators and prevents them from being overwritten through fleet.yaml or BundleDeployment options.

Patched versions of Fleet include releases v0.15.2, v0.14.6, v0.13.11, and v0.12.15.

Workarounds

If you can’t immediately upgrade to a patched version, use one of the following workarounds:

1 - Deploy NeuVector(primary workaround)

Deploy NeuVector (SUSE Security) and configure an admission control Deny rule for "Run as privileged" in Protect mode.

• NeuVector evaluates pod specs independently of Kubernetes PSS namespace labels. It blocks privileged containers even if the labels are downgraded.
• Although the namespace labels are still overwritten, the attack cannot exploit confidentiality, integrity, or availability without a privileged pod.

2 - Restrict repository access (secondary workaround)

Note: The following measure reduces the attack surface but does not close the vulnerability:

• In a multi-tenant setup, this restriction removes the primary attack vector. However, this measure only reduces the attack surface and doesn't completely close the vulnerability. It may also not be operationally viable for all organizations. ´

Credits

This security issue was reported by the following collaborators according to our responsible disclosure policy:

• Radisauskas Arnoldas from NATO and the NATO Cyber Security Centre (NCSC).

References

• Reach out to the SUSE Rancher Security team for security related inquiries.
• Open an issue in the Rancher repository.
• Verify with our support matrix and product support lifecycle.

Affected packages

• github.com/rancher/fleet >= 0.15.0, < 0.15.2
• github.com/rancher/fleet >= 0.14.0, < 0.14.6
• github.com/rancher/fleet >= 0.13.0, < 0.13.11
• github.com/rancher/fleet >= 0.12.0, < 0.12.15

Remediation

Upgrade to a patched release:

• github.com/rancher/fleet 0.15.2
• github.com/rancher/fleet 0.14.6
• github.com/rancher/fleet 0.13.11
• github.com/rancher/fleet 0.12.15