Privilege escalation to cluster admin on multi-tenant environments

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.8 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2021-41254: 1.82% estimated exploitation activity in the next 30 days; percentile 78.83 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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. Impact Multitenant environments where non-admin users have permissions to create Flux Kustomization objects are affected by this issue. Exploit To exploit the command injection, first we create a secret with a shell command: Then we create a Service Account that refers to the above Secret: And finally a Kustomization that runs under the above Service Account: When kustomize-controller reconciles the above Kustomization, it will execute the shell command from the secret. Patches 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,…

Published by the source

15 Nov 2021, 17:35 UTC

Last modified by the source

1 Feb 2023, 05:06 UTC

Source last checked

26 Oct 2026, 14:54 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-35rf-v2jv-gfg7

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# Patch Next advisory brief: CVE-2021-41254

Advisory: Privilege escalation to cluster admin on multi-tenant environments
IDs: CVE-2021-41254, GHSA-35rf-v2jv-gfg7
Record: https://patchnext.com/advisories/cve-2021-41254 (revision 1, source checked 26 Oct 2026, 14:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/fluxcd/kustomize-controller 0.15.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/fluxcd/kustomize-controller: affected < 0.15.0; fixed in 0.15.0

## Suggested inspection (read-only)
- Go github.com/fluxcd/kustomize-controller: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/fluxcd/kustomize-controller.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-35rf-v2jv-gfg7 (GitHub-reviewed advisory GHSA-35rf-v2jv-gfg7 lists affected ranges: Go github.com/fluxcd/kustomize-controller >=0 <0.15.0)

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