Flux2 is a tool for keeping Kubernetes clusters in sync with sources of configuration, and Flux's helm-controller is a Kubernetes operator that allows one to declaratively manage Helm chart releases. Helm controller is tightly integrated with the Helm SDK. A vulnerability found in the Helm SDK that affects flux2 v0.0.17 until v0.32.0 and helm-controller v0.0.4 until v0.23.0 allows for specific data inputs to cause high memory consumption. In some platforms, this could cause the controller to panic and stop processing reconciliations. In a shared cluster multi-tenancy environment, a tenant could create a HelmRelease that makes the controller panic, denying all other tenants from their Helm releases being reconciled. Patches are available in flux2 v0.32.0 and helm-controller v0.23.0.

Flux is an open and extensible continuous delivery solution for Kubernetes. Path Traversal in the kustomize-controller via a malicious `kustomization.yaml` allows an attacker to cause a Denial of Service at the controller level. Workarounds include automated tooling in the user's CI/CD pipeline to validate `kustomization.yaml` files conform with specific policies. This vulnerability is fixed in kustomize-controller v0.24.0 and included in flux2 v0.29.0. Users are recommended to upgrade.

Flux is an open and extensible continuous delivery solution for Kubernetes. Path Traversal in the kustomize-controller via a malicious `kustomization.yaml` allows an attacker to expose sensitive data from the controller’s pod filesystem and possibly privilege escalation in multi-tenancy deployments. Workarounds include automated tooling in the user's CI/CD pipeline to validate `kustomization.yaml` files conform with specific policies. This vulnerability is fixed in kustomize-controller v0.24.0 and included in flux2 v0.29.0.

Flux2 is an open and extensible continuous delivery solution for Kubernetes. Flux2 versions between 0.1.0 and 0.29.0, helm-controller 0.1.0 to v0.19.0, and kustomize-controller 0.1.0 to v0.23.0 are vulnerable to Code Injection via malicious Kubeconfig. In multi-tenancy deployments this can also lead to privilege escalation if the controller's service account has elevated permissions. Workarounds include disabling functionality via Validating Admission webhooks by restricting users from setting the `spec.kubeConfig` field in Flux `Kustomization` and `HelmRelease` objects. Additional mitigations include applying restrictive AppArmor and SELinux profiles on the controller’s pod to limit what binaries can be executed. This vulnerability is fixed in kustomize-controller v0.23.0 and helm-controller v0.19.0, both included in flux2 v0.29.0

kustomize-controller is a Kubernetes operator, specialized in running continuous delivery pipelines for infrastructure and workloads defined with Kubernetes manifests and assembled with Kustomize. Users that can create Kubernetes Secrets, Service Accounts and Flux Kustomization objects, could execute commands inside the kustomize-controller container by embedding a shell script in a Kubernetes Secret. This can be used to run `kubectl` commands under the Service Account of kustomize-controller, thus allowing an authenticated Kubernetes user to gain cluster admin privileges. In affected versions multitenant environments where non-admin users have permissions to create Flux Kustomization objects are affected by this issue. This vulnerability was fixed in kustomize-controller v0.15.0 (included in flux2 v0.18.0) released on 2021-10-08. Starting with v0.15, the kustomize-controller no longer executes shell commands on the container OS and the `kubectl` binary has been removed from the container image. To prevent the creation of Kubernetes Service Accounts with `secrets` in namespaces owned by tenants, a Kubernetes validation webhook such as Gatekeeper OPA or Kyverno can be used.