An actor with the ability to influence the contents of a bucket referenced by a Bucket resource can cause source-controller to write fetched object data to paths outside the per-reconciliation working directory.
The corruption surface is bounded by source-controller's own and downstream Flux controllers' digest verification: source-controller verifies stored artifact digests during reconciliation and rebuilds on divergence; consumers (kustomize-controller, helm-controller) verify the digest of fetched artifacts and reject mismatches. These checks prevent a manipulated artifact from reaching the cluster, but an attacker can still write files anywhere the source-controller pod has permission to write.
Separately, a user with permission to create or update GitRepository resources can cause source-controller to test for the existence of paths outside the cloned repository. Because the result is exposed via the resource's status, this allows limited enumeration of file paths on the controller pod. This surface exists only on source-controller v1.6.0 and later, where the sparse-checkout feature was introduced.
This vulnerability was fixed in source-controller v1.8.5.
There is no in-product workaround. Users should upgrade to a patched version.
As a defense-in-depth measure for the GitRepository sparse-checkout surface, a ValidatingAdmissionPolicy (or a third-party policy engine such as Kyverno or OPA Gatekeeper) can be deployed to reject GitRepository resources whose .spec.sparseCheckout entries contain .. or absolute path segments.
The path traversal in the Bucket reconciler was reported by JUNYI LIU. The path traversal in the GitRepository sparse-checkout validation was found and patched by the Flux engineering team.
If you have any questions or comments about this advisory:
| Software | From | Fixed in |
|---|---|---|
github.com/fluxcd/source-controller
|
0.0.17 | 1.8.5 |
A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.
Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.
Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
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