OPenFGA is an open source authorization/permission engine built for developers. OpenFGA versions v1.1.0 and prior are vulnerable to a DoS attack when Check and ListObjects calls are executed against authorization models that contain circular relationship definitions. Users are affected by this vulnerability if they are using OpenFGA v1.1.0 or earlier, and if you are executing `Check` or `ListObjects` calls against a vulnerable authorization model. Users are advised to upgrade to version 1.1.1. There are no known workarounds for this vulnerability. Users that do not have circular relationships in their models are not affected.

Affected: Go: github.com/openfga/openfga

### Overview

OpenFGA versions v1.1.0 and prior are vulnerable to a DoS attack when certain Check and ListObjects calls are executed against authorization models that contain circular relationship definitions.

### Am I Affected?

You are affected by this vulnerability if you are using OpenFGA v1.1.0 or earlier, and if you are executing certain [Check](https://openfga.dev/api/service#/Relationship%20Queries/Check) or [ListObjects](https://openfga.dev/api/service#/Relationship%20Queries/ListObjects) calls against a vulnerable authorization model. To see which of your models could be vulnerable to this attack, download OpenFGA v1.2.0 and run the following command:

``` ./openfga validate-models --datastore-engine <ENGINE> --datastore-uri <URI> | jq .[] | select(.Error | contains("loop")) ```

replacing the variables `<ENGINE>` and `<URI>` as needed.

### Fix

Upgrade to v1.1.1.

### Backward Compatibility

If you are not passing an invalid authorization model (as identified by running `./openfga validate-models`) as a parameter of your Check and ListObjects calls, this upgrade is backwards compatible.

Otherwise, OpenFGA v1.1.1 will start returning HTTP 400 status codes on those calls.