The source-controller component of fluxcd, which manages artifact acquisition from external sources, suffers from a relative path traversal vulnerability (CWE-23) in versions 0.0.17 through 1.8.4. An attacker able to influence the contents of a bucket referenced by a Bucket resource can cause the controller to write fetched object data outside its designated working directory. Although digest verification by source-controller and downstream controllers limits the risk of manipulated artifacts reaching the cluster, arbitrary file writes on the controller pod remain possible within its permission scope. Separately, from version 1.6.0 onward, the sparse-checkout feature in GitRepository resources allows limited file path enumeration on the controller pod due to path existence tests exposed in resource status. This vulnerability was addressed in source-controller version 1.8.5. No in-product workaround is available, but deploying a ValidatingAdmissionPolicy or third-party policy engine to restrict sparseCheckout entries can provide defense-in-depth.

An attacker with the ability to influence bucket contents can write files anywhere the source-controller pod has write permissions, potentially leading to unauthorized file modifications or persistence on the pod. The digest verification mechanisms prevent manipulated artifacts from propagating to the cluster, limiting the risk of cluster compromise via this vector. The sparse-checkout path enumeration vulnerability allows users with GitRepository resource permissions to gain limited knowledge of the pod's filesystem, which could aid further attacks. There are no known exploits in the wild.

A fixed version (source-controller v1.8.5) is available and users should upgrade to this or later versions to remediate the vulnerability. There is no in-product workaround. As a defense-in-depth measure for the sparse-checkout path enumeration, administrators can deploy a ValidatingAdmissionPolicy or third-party policy engines such as Kyverno or OPA Gatekeeper to reject GitRepository resources whose .spec.sparseCheckout entries contain relative path segments like '..' or absolute paths.