===================================================================                             CERT-Renater

                  Note d'Information No. 2023/VULN233

_____________________________________________________________________

DATE                : 23/06/2023

HARDWARE PLATFORM(S): /

OPERATING SYSTEM(S): Systems running kube-apiserver versions prior to
                              1.27.3, 1.26.6, 1.25.11, 1.24.15.

====================================================================https://groups.google.com/g/kubernetes-security-announce/c/9oU_lW2cU_g
https://groups.google.com/g/kubernetes-security-announce/c/vPWYJ_L84m8
_____________________________________________________________________

[Security Advisory] CVE-2023-2728: Bypassing enforce mountable
secrets policy imposed by the ServiceAccount admission plugin


Hello Kubernetes Community,

A security issue was discovered in Kubernetes where users may be able
to launch containers that bypass the mountable secrets policy enforced
by the ServiceAccount admission plugin when using ephemeral
containers. The policy ensures pods running with a service account
may only reference secrets specified in the service account’s secrets
field. Kubernetes clusters are only affected if the ServiceAccount
admission plugin and the kubernetes.io/enforce-mountable-secrets
annotation are used together with ephemeral containers.

This issue has been rated Medium

(CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N), and assigned
CVE-2023-2728


Am I vulnerable?
Clusters are impacted by this vulnerability if all of the
following are true:

     The ServiceAccount admission plugin is used. Most cluster
should have this on by default as recommended in
https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/#serviceaccount
     The kubernetes.io/enforce-mountable-secrets annotation
is used by a service account. This annotation is not added
by default.

     Pods are using ephemeral containers.


Affected Versions

     kube-apiserver v1.27.0 - v1.27.2
     kube-apiserver v1.26.0 - v1.26.5
     kube-apiserver v1.25.0 - v1.25.10
     kube-apiserver <= v1.24.14


How do I mitigate this vulnerability?
This issue can be mitigated by applying the patch provided for
the kube-apiserver component. The patch prevents ephemeral
containers from bypassing the mountable secrets policy enforced
by the ServiceAccount admission plugin.


Fixed Versions

     kube-apiserver v1.27.3
     kube-apiserver v1.26.6
     kube-apiserver v1.25.11
     kube-apiserver v1.24.15

These releases have been published today, June 14th, 2023.

Detection
Pod update requests using an ephemeral container that exploits
this vulnerability with unintended secret will be captured in
API audit logs. You can also use kubectl get pods to find active
pods with ephemeral containers running with a secret that is not
referenced by the service account in your cluster.


Additional Details
See the GitHub issue for more details:
https://github.com/kubernetes/kubernetes/issues/118640


Thank You,
Rita Zhang on behalf of the Kubernetes Security Response Committee

_____________________________________________________________________

[Security Advisory] CVE-2023-2727: Bypassing policies imposed by the


Hello Kubernetes Community,

A security issue was discovered in Kubernetes where users may be
able to launch containers using images that are restricted by
ImagePolicyWebhook when using ephemeral containers. Kubernetes
clusters are only affected if the ImagePolicyWebhook admission
plugin is used together with ephemeral containers.

This issue has been rated Medium
(CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N), and assigned
CVE-2023-2727


Am I vulnerable?
Clusters are impacted by this vulnerability if all of the following
are true:

     The ImagePolicyWebhook admission plugin is used to restrict
use of certain images
     Pods are using ephemeral containers.


Affected Versions

     kube-apiserver v1.27.0 - v1.27.2
     kube-apiserver v1.26.0 - v1.26.5
     kube-apiserver v1.25.0 - v1.25.10
     kube-apiserver <= v1.24.14

How do I mitigate this vulnerability?
This issue can be mitigated by applying the patch provided for the
kube-apiserver component. This patch prevents ephemeral containers
from using an image that is restricted by ImagePolicyWebhook.
Note: Validation webhooks (such as Gatekeeper and Kyverno) can also
be used to enforce the same restrictions.


Fixed Versions

     kube-apiserver v1.27.3
     kube-apiserver v1.26.6
     kube-apiserver v1.25.11
     kube-apiserver v1.24.15

These releases have been published today, June 14th, 2023.


Detection
Pod update requests using an ephemeral container with an image
that should have been restricted by an ImagePolicyWebhook will
be captured in API audit logs. You can also use `kubectl get
pods` to find active pods with ephemeral containers running
an image that should have been restricted in your cluster with
this issue.


Additional Details
See the GitHub issue for more details:
https://github.com/kubernetes/kubernetes/issues/118640

Thank You,
Rita Zhang on behalf of the Kubernetes Security Response
Committee


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