Argo CD is a declarative, GitOps continuous delivery tool for Kubernetes. Argo CD starting with version 0.7.0 and prior to versions 2.1.15m 2.2.9, and 2.3.4 is vulnerable to a symlink following bug allowing a malicious user with repository write access to leak sensitive files from Argo CD's repo-server. A malicious Argo CD user with write access for a repository which is (or may be) used in a directory-type Application may commit a symlink which points to an out-of-bounds file. Sensitive files which could be leaked include manifest files from other Applications' source repositories (potentially decrypted files, if you are using a decryption plugin) or any JSON-formatted secrets which have been mounted as files on the repo-server. A patch for this vulnerability has been released in Argo CD versions 2.3.4, 2.2.9, and 2.1.15. Users of versions 2.3.0 or above who do not have any Jsonnet/directory-type Applications may disable the Jsonnet/directory config management tool as a workaround.

Impact

All versions of Argo CD starting with v0.7.0 are vulnerable to an uncontrolled memory consumption bug, allowing an authorized malicious user to crash the repo-server service. The repo-server is a critical component of Argo CD, so crashing the repo-server effectively denies core Argo CD services (such as syncing Application updates).

To achieve denial of service, the attacker must be an authenticated Argo CD user authorized to deploy Applications from a repository which contains (or can be made to contain) a large file.

Patches

A patch for this vulnerability has been released in the following Argo CD versions:

v2.4.1 v2.3.5 v2.2.10 v2.1.16

The patch introduces a new reposerver.max.combined.directory.manifests.size config parameter, which you should tune before upgrading in production. It caps the maximum total file size of .yaml/.yml/.json files in directory-type (raw manifest) Applications. The default max is 10M per Application. This max is designed to keep any single app from consuming more than 3G of memory in the repo-server (manifests consume more space in memory than on disk). The 300x ratio assumes a maliciously-crafted manifest file. If you only want to protect against accidental excessive memory use, it is probably safe to use a smaller ratio.

If your organization uses directory-type Applications with very many manifests or very large manifests then check the size of those manifests and tune the config parameter before deploying this change to production. When testing, make sure to do a "hard refresh" in either the CLI or UI to test your directory-type App. That will make sure you're using the new max logic instead of relying on cached manifest responses from Redis.

Workarounds

There is no workaround besides upgrading.

To mitigate the issue, carefully limit 1) who can configure repos (determined by RBAC), 2) which repos are allowed (determined by Project limitations), and 3) who has push access to those repos (determined by your SCM provider configuration).

Credits

Disclosed by ADA Logics in a security audit of the Argo project sponsored by CNCF and facilitated by OSTIF. Thanks to Adam Korczynski and David Korczynski for their work on the audit.

For more information

Open an issue in the Argo CD issue tracker or discussions Join us on Slack in channel #argo-cd