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                                  CERT-Renater

                        Note d'Information No. 2023/VULN450

_____________________________________________________________________

DATE                : 06/11/2023

HARDWARE PLATFORM(S): /

OPERATING SYSTEM(S): Systems running kubelet versions prior to 1.28.1,
                            1.27.5, 1.26.8, 1.25.13, 1.24.17.

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https://groups.google.com/g/kubernetes-security-announce/c/JrX4bb7d83E
_____________________________________________________________________

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


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-2023-3955**


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 (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 secu...@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


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