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.
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.
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.
The Flux engineering team found and patched this vulnerability.