Date: Fri, 22 Apr 2022 09:37:42 -0700 From: CJ Cullen <cjcullen@...gle.com> To: oss-security@...ts.openwall.com Subject: [kubernetes] CVE-2021-25746: Ingress-nginx directive injection via annotations Issue Details A security issue was discovered in ingress-nginx <https://github.com/kubernetes/ingress-nginx> where a user that can create or update ingress objects can use `.metadata.annotations` in 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 <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-2021-25746. 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 `metadata.annotations` values to known safe (see the newly added rules <https://github.com/kubernetes/ingress-nginx/blame/main/internal/ingress/inspector/rules.go>, or the suggested value for annotation-value-word-blocklist <https://kubernetes.github.io/ingress-nginx/user-guide/nginx-configuration/configmap/#annotation-value-word-blocklist> ). Detection If you find evidence that this vulnerability has been exploited, please contact security@...ernetes.io Additional Details See ingress-nginx Issue #8503 <https://github.com/kubernetes/ingress-nginx/issues/8503> for more details. Acknowledgements This vulnerability was reported by Anthony Weems, and separately by jeffrey&oliver. Thank You, CJ Cullen on behalf of the Kubernetes Security Response Committee
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