[kubernetes] CVE-2023-3955: Insufficient input sanitization on Windows nodes leads to privilege escalation

[Rita Zhang <rita.z.zhang () gmail com>]

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
<https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H>
-
8.8
<https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H>),
and assigned **CVE-2023-3955**

*Am I vulnerable?*

Any kubernetes environment with Windows nodes is impacted.  Run `kubectl
get nodes -l kubernetes.io/os=windows` <http://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 (see fix impact
below).  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 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.

***Fix impact:*** Passing Windows Powershell disk format options to in-tree
volume plugins will result in an error during volume provisioning on the
node.  There are no known use cases for this functionality, nor is this
functionality supported by any known out-of-tree CSI driver.

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.

If you find evidence that this vulnerability has been exploited, please
contact security () kubernetes io

*Additional Details*

See the GitHub issue for more details:
https://github.com/kubernetes/kubernetes/issues/119595

*Acknowledgements*

This vulnerability was discovered by James Sturtevant @jsturtevant and Mark
Rossetti @marosset during the process of fixing CVE-2023-3676 (that
original CVE 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