Improper path handling in Kustomization files allows for denial of service

The kustomize-controller enables the use of Kustomize’s functionality when applying Kubernetes declarative state onto a cluster. A malicious user can use a specially crafted kustomization.yaml to cause Denial of Service at controller level.

In multi-tenancy deployments this can lead to multiple tenants not being able to apply their Kustomizations until the malicious kustomization.yaml is removed and the controller restarted.

Impact

Within the affected versions, users with write access to a Flux source are able to craft a malicious kustomization.yaml file which causes the controller to enter an endless loop.

Patches

This vulnerability was fixed in kustomize-controller v0.24.0 and included in flux2 v0.29.0 released on 2022-04-20. The changes introduce better handling of Kustomization files blocking references that could lead to endless loops.

Credits

The Flux engineering team found and patched this vulnerability.

For more information

If you have any questions or comments about this advisory please open an issue in the flux2 repository.