Date: Fri, 10 Jun 2022 09:11:47 -0700 From: CJ Cullen <cjcullen@...gle.com> To: oss-security@...ts.openwall.com Subject: [kubernetes] CVE-2021-25748: Ingress-nginx `path` sanitization can be bypassed with newline character 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 a newline character to bypass the sanitization of 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 <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-2021-25748. 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), you are not affected. Multitenant environments where non-admin users have permissions to create Ingress objects are most affected by this issue. Affected Versions - <v1.2.1 Fixed Versions - v1.2.1 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 <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 #8686 <https://github.com/kubernetes/ingress-nginx/issues/8686> for more details. Acknowledgements This vulnerability was reported by Gafnit Amiga. Thank You, CJ Cullen on behalf of the Kubernetes Security Response Committee
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