ghsa-vvmq-fwmg-2gjc
Vulnerability from github
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 Kustomization or HelmRelease objects and Kubernetes Secrets.
- Direct access to the cluster to modify existing Kubernetes secrets being used as kubeconfig in existing Flux Kustomization or HelmRelease objects.
- Direct access to the cluster to modify existing Flux Kustomization or HelmRelease objects 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": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/fluxcd/flux2"
},
"ranges": [
{
"events": [
{
"introduced": "0.1.0"
},
{
"fixed": "0.29.0"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/fluxcd/kustomize-controller"
},
"ranges": [
{
"events": [
{
"introduced": "0.1.0"
},
{
"fixed": "0.23.0"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "github.com/fluxcd/helm-controller"
},
"ranges": [
{
"events": [
{
"introduced": "0.2.0"
},
{
"fixed": "0.19.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2022-24817"
],
"database_specific": {
"cwe_ids": [
"CWE-94"
],
"github_reviewed": true,
"github_reviewed_at": "2022-05-16T18:13:51Z",
"nvd_published_at": "2022-05-06T00:15:00Z",
"severity": "CRITICAL"
},
"details": "Flux2 can reconcile the state of a remote cluster when provided with a [kubeconfig](https://kubernetes.io/docs/concepts/configuration/organize-cluster-access-kubeconfig/#file-references) with the correct access rights. `Kubeconfig` files can define [commands](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#client-go-credential-plugins) 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\u2019s container.\n\nIn multi-tenancy deployments this can also lead to privilege escalation if the controller\u0027s service account has elevated permissions.\n\n### Impact\n\nWithin the affected versions range, one of the permissions set below would be required for the vulnerability to be exploited:\n- Direct access to the cluster to create Flux `Kustomization` or `HelmRelease` objects and Kubernetes Secrets.\n- Direct access to the cluster to modify existing Kubernetes secrets being used as `kubeconfig` in existing Flux `Kustomization` or `HelmRelease` objects.\n- Direct access to the cluster to modify existing Flux `Kustomization` or `HelmRelease` objects and access to create or modify existing Kubernetes secrets.\n- Access rights to make changes to a configured Flux Source (i.e. Git repository).\n\n### Patches\n\nThis vulnerability was fixed in kustomize-controller [v0.23.0](https://github.com/fluxcd/kustomize-controller/releases/tag/v0.23.0) and helm-controller [v0.19.0](https://github.com/fluxcd/helm-controller/releases/tag/v0.19.0), both included in flux2 [v0.29.0](https://github.com/fluxcd/flux2/releases/tag/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\u2019s command arguments. Users are no longer allowed to refer to files in the controller\u2019s filesystem in the `kubeconfig` files provided for the remote apply feature.\n\n### Workarounds\n\n- The functionality can be disabled via Validating Admission webhooks (e.g. OPA Gatekeeper, Kyverno) by restricting users from being able to set the `spec.kubeConfig` field in Flux `Kustomization` and `HelmRelease` objects.\n- Applying restrictive AppArmor and SELinux profiles on the controller\u2019s pod to limit what binaries can be executed.\n\n### Credits\n\nThe Flux engineering team found and patched this vulnerability.\n\n### For more information\n\nIf you have any questions or comments about this advisory please open an issue in the [flux2 repository](http://github.com/fluxcd/flux2).\n",
"id": "GHSA-vvmq-fwmg-2gjc",
"modified": "2022-05-26T20:07:54Z",
"published": "2022-05-16T18:13:51Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/fluxcd/flux2/security/advisories/GHSA-vvmq-fwmg-2gjc"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-24817"
},
{
"type": "PACKAGE",
"url": "https://github.com/fluxcd/flux2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "Improper kubeconfig validation allows arbitrary code execution"
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.