GHSA-vvmq-fwmg-2gjc
CRITICALImproper kubeconfig validation allows arbitrary code execution
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
github.com/fluxcd/flux2🐹github.com/fluxcd/kustomize-controller🐹github.com/fluxcd/helm-controllerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Flux2 can reconcile the state of a remote cluster when provided with a kubeconfig with the correct access rights. Kubeconfig files can define commands to be executed to generate on-demand authentication tokens. A malicious user with write access to a Flux source or direct access to the target cluster, could craft a kubeconfig to execute arbitrary code inside the controller’s container.
In multi-tenancy deployments this can also lead to privilege escalation if the controller's service account has elevated permissions.
Impact
Within the affected versions range, one of the permissions set below would be required for the vulnerability to be exploited:
- Direct access to the cluster to create Flux
KustomizationorHelmReleaseobjects and Kubernetes Secrets. - Direct access to the cluster to modify existing Kubernetes secrets being used as
kubeconfigin existing FluxKustomizationorHelmReleaseobjects. - Direct access to the cluster to modify existing Flux
KustomizationorHelmReleaseobjects and access to create or modify existing Kubernetes secrets. - Access rights to make changes to a configured Flux Source (i.e. Git repository).
Patches
This vulnerability was fixed in kustomize-controller v0.23.0 and helm-controller v0.19.0, both included in flux2 v0.29.0. Starting from the fixed versions, both controllers disable the use of command execution from kubeconfig files by default, users have to opt-in by adding the flag --insecure-kubeconfig-exec to the controller’s command arguments. Users are no longer allowed to refer to files in the controller’s filesystem in the kubeconfig files provided for the remote apply feature.
Workarounds
- The functionality can be disabled via Validating Admission webhooks (e.g. OPA Gatekeeper, Kyverno) by restricting users from being able to set the
spec.kubeConfigfield in FluxKustomizationandHelmReleaseobjects. - Applying restrictive AppArmor and SELinux profiles on the controller’s pod to limit what binaries can be executed.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/fluxcd/flux2 | ≥ 0.1.0&&< 0.29.0 | 0.29.0 |
| 🐹Go | github.com/fluxcd/kustomize-controller | ≥ 0.1.0&&< 0.23.0 | 0.23.0 |
| 🐹Go | github.com/fluxcd/helm-controller | ≥ 0.2.0&&< 0.19.0 | 0.19.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/fluxcd/flux2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/fluxcd/flux2 to 0.29.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vvmq-fwmg-2gjc is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-vvmq-fwmg-2gjc is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-vvmq-fwmg-2gjc. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-vvmq-fwmg-2gjc in your dependencies?
O3 detects GHSA-vvmq-fwmg-2gjc across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.