### Summary

ZITADEL Action V2 (introduced as early preview in 2.59.0, beta in 3.0.0 and GA in 4.0.0) is a webhook based approach to allow developers act on API request to Zitadel and customize flows such the issue of a token.

ZITADEL's Action target URLs can point to local hosts, potentially allowing adversaries to gather internal network information and connect to internal services.

### Impact

When the URL points to a local host / IP address, an adversary might gather information about the internal network structure, the services exposed on internal hosts etc. This is sometimes called a Server-Side Request Forgery (SSRF).

ZITADEL Actions expect responses according to specific schemas, which reduces the threat vector.

### Affected Versions

Systems running one of the following versions are affected:
- **4.x**: `4.0.0` through `4.11.0` (including RC version)
- **3.x**: `3.0.0` to `3.4.6` (including RC versions)
- **2.x**: `2.59.0` to `2.71.19`

### Patches

The vulnerability has been addressed in the latest releases. The patch resolves the issue by checking the target URL against a denylist. By default localhost, resp. loopback IPs are denied.

Note that this fix was only released on v4.x. Due to the stage (preview / beta) in which the functionality was in v2.x and v3.x, the changes that have been applied to it since then and the severity, respectively the actual thread vector, a backport to the corresponding versions was not feasible. Please check the workaround section for alternative solutions if an upgrade to v4.x is not possible.

4.x: Upgrade to >=[4.11.1](https://github.com/zitadel/zitadel/releases/tag/v4.11.1)
3.x: Update to >=[v4.11.1](https://github.com/zitadel/zitadel/releases/tag/v4.11.1) or check out workarounds
2.x: Update to >=[v4.11.1](https://github.com/zitadel/zitadel/releases/tag/v4.11.1) or check out workarounds

### Workarounds

The recommended solution is to update Zitadel to a patched version.

If an upgrade is not possible, users can prevent actions from using unintended endpoints by setting network policies or firewall rules in your infrastructure. Note that this is outside of the functionality provided by ZITADEL.

### Questions

If there are any questions or comments about this advisory, please send an email to [[email protected]](mailto:[email protected])

### Credits

This vulnerability was found by [zentrust partners GmbH](https://zentrust.partners) during a scheduled penetration test. Thank you to the analysts Martin Tschirsich, Joud Zakharia, Christopher Baumann.
The full report will be made public after the complete review.

CWE-918 Server-Side Request Forgery (SSRF)