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List: oss-security
Subject: [oss-security] [kubernetes] CVE-2021-25745: Ingress-nginx `path` can be pointed to service account t
From: CJ Cullen <cjcullen () google ! com>
Date: 2022-04-22 16:37:40
Message-ID: CABdrxGC5N9J4TqhzAOVpKuFkYijWREVtj5ToB5aD+GQx-YDsJA () mail ! gmail ! com
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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 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-2021-25745.
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
<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@kubernetes.io
Additional Details
See ingress-nginx Issue #8502
<https://github.com/kubernetes/ingress-nginx/issues/8502>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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