[Security Advisory] CVE-2023-3676: Insufficient input sanitization on Windows nodes leads to privilege escalation

[Rita Zhang]

Hello Kubernetes Community,

A security issue was discovered in Kubernetes where a user that can create pods on Windows nodes may be able to escalate to admin privileges on those nodes. Kubernetes clusters are only affected if they include Windows nodes.

This issue has been rated **HIGH** (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - 8.8), and assigned **CVE-2023-3676**

Am I vulnerable?

Any kubernetes environment with Windows nodes is impacted.  Run `kubectl get nodes -l kubernetes.io/os=windows` to see if any Windows nodes are in use.

Affected Versions

- kubelet <= v1.28.0

- kubelet <= v1.27.4

- kubelet <= v1.26.7

- kubelet <= v1.25.12

- kubelet <= v1.24.16

How do I mitigate this vulnerability?

The provided patch fully mitigates the vulnerability and has no known side effects.  Full mitigation for this class of issues requires patches applied for CVE-2023-3676, CVE-2023-3955, and CVE-2023-3893.

Outside of applying the provided patch, there are no known mitigations to this vulnerability.

Fixed Versions

- kubelet v1.28.1

- kubelet v1.27.5

- kubelet v1.26.8

- kubelet v1.25.13

- kubelet v1.24.17

These releases will be published over the course of today, August 23rd, 2023.

To upgrade, refer to the documentation:

https://kubernetes.io/docs/tasks/administer-cluster/cluster-management/#upgrading-a-cluster

Detection

Kubernetes audit logs can be used to detect if this vulnerability is being exploited. Pod create events with embedded powershell commands are a strong indication of exploitation. Config maps and secrets that contain embedded powershell commands and are mounted into pods are also a strong indication of exploitation.

If you find evidence that this vulnerability has been exploited, please contact secu...@kubernetes.io

Additional Details

See the GitHub issue for more details: https://github.com/kubernetes/kubernetes/issues/119339

Acknowledgements

This vulnerability was reported by Tomer Peled @tomerpeled92

The issue was fixed and coordinated by the fix team: 

James Sturtevant @jsturtevant

Mark Rossetti @marosset

Andy Zhang @andyzhangx

Justin Terry @jterry75

Kulwant Singh @KlwntSingh

Micah Hausler @micahhausler

Rita Zhang @ritazh

and release managers:

Jeremy Rickard @jeremyrickard

Thank You,

Rita Zhang on behalf of the Kubernetes Security Response Committee