Fwd: [Security Advisory] CVE-2021-25745: Ingress-nginx `path` can be pointed to service account token file
CJ Cullen
From: CJ Cullen <cjcu...@google.com>
Date: Fri, Apr 22, 2022 at 9:31 AM
Subject: [Security Advisory] CVE-2021-25745: Ingress-nginx `path` can be pointed to service account token file
To: <kubernete...@googlegroups.com>, kubernetes-dev <kuberne...@googlegroups.com>, <kubernetes-sec...@googlegroups.com>, <kubernetes-se...@googlegroups.com>, <distributo...@kubernetes.io>, <kubernetes+a...@discoursemail.com>
Issue Details
A security issue was discovered in ingress-nginx where a user that can create or update ingress objects can use the `spec.rules[].http.paths[].path` field of an Ingress object (in the `networking.k8s.io` or `extensions` API group) to 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), and assigned CVE-2021-25745.
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`.
Multitenant environments where non-admin users have permissions to create Ingress objects are most affected by this issue.
Affected Versions
<v1.2.0
Fixed Versions
v1.2.0-beta.0
v1.2.0
Mitigation
If you are unable to roll out the fix, this vulnerability can be mitigated by implementing an admission policy that restricts the `spec.rules[].http.paths[].path` field on the networking.k8s.io/Ingress resource to known safe characters (see the newly added rules, or the suggested value for annotation-value-word-blocklist).
Detection
If you find evidence that this vulnerability has been exploited, please contact secu...@kubernetes.io
Additional Details
See ingress-nginx Issue #8502 for more details.
Acknowledgements
This vulnerability was reported by Gafnit Amiga.
Thank You,
CJ Cullen on behalf of the Kubernetes Security Response Committee