oss-security - [kubernetes] CVE-2023-5043: Ingress nginx annotation injection causes arbitrary command execution

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Date: Wed, 25 Oct 2023 09:32:11 -0700
From: CJ Cullen <cjcullen@...gle.com>
To: oss-security@...ts.openwall.com
Subject: [kubernetes] CVE-2023-5043: Ingress nginx annotation injection causes
 arbitrary command execution

Issue Details

A security issue was identified in ingress-nginx
<https://github.com/kubernetes/ingress-nginx> where the
nginx.ingress.kubernetes.io/configuration-snippet annotation on an Ingress
object (in the `networking.k8s.io` or `extensions` API group) can be used
to inject arbitrary commands, and obtain the credentials of the
ingress-nginx controller. In the default configuration, that credential has
access to all secrets in the cluster.

This issue has been rated High (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L
<https://www.first.org/cvss/calculator/3.1#CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L>),
and assigned CVE-2023-5043.
Affected Components and Configurations

This bug affects ingress-nginx. If you do not have ingress-nginx installed
on your cluster, you are not affected. You can check this by running
`kubectl get po -n ingress-nginx`.

If you are running the “chrooted” ingress-nginx controller introduced in
v1.2.0 (gcr.io/k8s-staging-ingress-nginx/controller-chroot), command
execution is possible but credential extraction is not, so the High
severity does not apply.

Multi-tenant environments where non-admin users have permissions to create
Ingress objects are most affected by this issue.
Affected Versions

   -

   <v1.9.0

Versions allowing mitigation

   -

   v1.9.0

Mitigation

Ingress Administrators should set the --enable-annotation-validation flag
to enforce restrictions on the contents of ingress-nginx annotation fields.
Detection

If you find evidence that this vulnerability has been exploited, please
contact security@...ernetes.io
Additional Details

See ingress-nginx Issue #10571
<https://github.com/kubernetes/ingress-nginx/issues/10571> for more details.
Acknowledgements

This vulnerability was reported by suanve

Thank You,

CJ Cullen on behalf of the Kubernetes Security Response Committee

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