Argo CD is a popular, declarative, GitOps continuous delivery tool for Kubernetes used to easily manage and deploy applications to your Kubernetes clusters. However, a recent vulnerability (CVE-2025-23216) has been discovered in Argo CD, which exposes secret values in error messages and the diff view when syncing an invalid Kubernetes Secret resource from a repository.

This post will examine the vulnerability in detail, provide a code snippet to demonstrate the exposure of secret data, share links to original references, and offer guidance on how to patch the issue and prevent future exploitation.

Exploit Details

The vulnerability assumes that an attacker has commit access to a repository that Argo CD is configured to sync from. By committing an invalid Kubernetes Secret resource to the repository and triggering a sync in Argo CD, it becomes possible for the attacker to expose secret values to any user with read access to the Argo CD instance.

Here's an example of a Kubernetes Secret with an invalid base64-encoded value

apiVersion: v1
kind: Secret
metadata:
  name: my-secret
type: Opaque
data:
  secret-key: bWFsaWNpb3VzX3ZhbHVl # This value is not valid base64

Upon syncing this invalid Secret, Argo CD will generate an error message containing the decoded secret data, such as:

failed to sync: Secret "my-secret" is invalid: data[secret-key]:
Invalid value: "bWFsaWNpb3VzX3ZhbHVl": invalid base64 data at input byte 2

Additionally, the diff view will also expose the decoded secret value along with other resource information:

apiVersion: v1
kind: Secret
metadata:
  name: my-secret
type: Opaque
data:
+ secret-key: bWFsaWNpb3VzX3ZhbHVl

Patching and Mitigation

The Argo CD team has issued patches for this vulnerability in versions v2.13.4, v2.12.10, and v2.11.13. You can find the official release notes, specific to this issue, in the following links:

- Release v2.13.4
- Release v2.12.10
- Release v2.11.13

It is highly recommended that you upgrade your Argo CD installations to one of the patched versions as soon as possible. Additionally, consider applying the principle of least privilege for your users, ensuring that only trusted users have write access to repositories from which Argo CD syncs resources.

Although the patches prevent the exposure of secret values in both error messages and the diff view, it is good practice to avoid using base64-encoded secrets directly in Git repositories. Instead, consider using an external secret management solution (for example, HashiCorp Vault or AWS Secrets Manager) to securely store and access secret values in your Kubernetes clusters.

Conclusion

The recent CVE-2025-23216 vulnerability exposed sensitive secret data in Argo CD error messages and diff views when syncing from a repository containing an invalid Kubernetes Secret resource. By upgrading your Argo CD installation to v2.13.4, v2.12.10, or v2.11.13, you can effectively patch this security issue and reduce the risk of secret data exposure. Remember to practice good security hygiene by limiting write access to trusted users and utilizing reliable secret management solutions for your Kubernetes clusters.

Stay informed about current and future vulnerabilities in Argo CD and other critical tools by subscribing to reliable security news sources and keeping an eye on updates from the Argo CD team via GitHub and their official website.

Timeline

Published on: 01/30/2025 16:15:31 UTC