CVE-2021-25749: runAsNonRoot logic bypass for Windows containers

[pacoxu]

What happened?

A security issue was discovered in Kubernetes that could allow Windows workloads to run as ContainerAdministrator even when those workloads set the runAsNonRoot option to true .

This issue has been rated low and assigned CVE-2021-25749

What did you expect to happen?

Detection

Kubernetes Audit logs may indicate if the user name was misspelled to bypass the restriction placed on which user is a pod allowed to run as.

If you find evidence that this vulnerability has been exploited, please contact [email protected]

Additional Details

See the GitHub issue for more details: kubernetes/kubernetes#112192

Acknowledgements

This vulnerability was reported and fixed by Mark Rosetti (@marosset)

CVSS Rating: Low (3.4) CVSS:3.1/AV:A/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C

How can we reproduce it (as minimally and precisely as possible)?

Am I vulnerable?

All Kubernetes clusters with following versions, running Windows workloads with runAsNonRoot are impacted

Anything else we need to know?

Affected Versions

• kubelet v1.20 - v1.21
• kubelet v1.22.0 - v1.22.13
• kubelet v1.23.0 - v1.23.10
• kubelet v1.24.0 - v1.24.4

How do I mitigate this vulnerability?
There are no known mitigations to this vulnerability.

Fixed Versions

• kubelet v1.22.14
• kubelet v1.23.11
• kubelet v1.24.5
• kubelet v1.25.0

To upgrade, refer to this documentation For core Kubernetes: https://kubernetes.io/docs/tasks/administer-cluster/cluster-management/#upgrading-a-cluster

[github-actions]

Hi @pacoxu,
Thanks for opening an issue!
We will look into it as soon as possible.

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