CVE-2026-79767: Gardener authorization bypass via group subject injection

CVE-2026-79767 · Severity: medium · CVSS 5.5 · Published 2026-09-22

Gardener is an open-source Kubernetes cluster management platform. An authorization flaw in its API server allows a project administrator without explicit member-management permissions to grant full project access to arbitrary user groups—including all authenticated users—by injecting group subjects into the project member list. This bypasses the intended access control, potentially exposing cluster credentials and workload data to unauthorized users.

Technologies: github.com/gardener/gardener (Go). Vendors: Go.

Quick answers

Is CVE-2026-79767 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-79767 being exploited in the wild.
How severe is CVE-2026-79767?
Medium severity, with a CVSS score of 5.5, published 22 September 2026.
Which products and versions are affected?
Gardener all versions before fix; gardener/gardener (Go) SEMVER:introduced=1.143.0,fixed=1.143.3; github.com/gardener/gardener (Go) SEMVER:introduced=0, SEMVER:introduced=0,fixed=1.142.6.
Is there a fix for CVE-2026-79767?
Yes. gardener/gardener (Go): upgrade to 1.143.3 or later; github.com/gardener/gardener (Go): upgrade to 1.142.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-79767 attacked?
It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-79767?
Check whether you run Gardener, gardener/gardener (Go) or github.com/gardener/gardener (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • gardener/gardener (Go): upgrade to 1.143.3 or later
    go get gardener/gardener@v1.143.3
  • github.com/gardener/gardener (Go): upgrade to 1.142.6 or later
    go get github.com/gardener/gardener@v1.142.6

Technical details

The vulnerability is an authorization bypass in the `customverbauthorizer` admission plugin's `manage-members` check. The `mustCheckProjectMembers()` function compares old and new project member lists but only examines `User`-kind subjects (via the `isHumanUser()` function), ignoring `Group`-kind subjects. An authenticated project administrator can leverage this blind spot to add arbitrary groups—such as `system:authenticated` (all authenticated users) or `system:unauthenticated`—to the project member list without triggering the authorization gate. The attack requires project admin role but no `manage-members` permission; it is network-accessible and requires only valid Kubernetes authentication. The impact is privilege escalation and unauthorized access to all project resources, including Shoots and cloud provider secrets.

Affected products

  • Gardener Gardener all versions before fix

Identifiers

  • CVE-2026-79767
  • GHSA-gfjv-gqf2-c888
  • GO-2026-6568

Timeline

  • 2026-09-22: disclosed
  • other: CVE-2026-79767 assigned

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.