A security issue was discovered in 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.
### 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@kubernetes.io](mailto:security@kubernetes.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
CVE-2021-25746: Ingress-nginx directive injection via annotations
This is a GitHub Issue
repo:ingress-nginx
owner:kubernetes
Title : CVE-2021-25746: Ingress-nginx directive injection via annotations
Issue date:

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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 `.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@kubernetes.io](mailto:security@kubernetes.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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