CVE-2021-36775

Rancher's Failure to delete orphaned role bindings does not revoke project level access from group based authentication

Workarounds

Limit access in Rancher to trusted users. There is not a direct mitigation besides upgrading to the patched Rancher versions.

References

Cluster and project roles documentation for Rancher 2.6, 2.5 and 2.4.

For more information

If you have any questions or comments about this advisory:

• Reach out to SUSE Rancher Security team for security related inquiries.
• Open an issue in Rancher repository.
• Verify our support matrix and product support lifecycle.

This vulnerability only affects customers using group based authentication in Rancher versions up to and including 2.4.17, 2.5.11 and 2.6.2.

When removing a Project Role associated to a group from a project, the bindings that grant access to cluster scoped resources for those subjects do not get deleted. This happens due to an incomplete authorization logic check. A user who is a member of an affected group with authenticated access to Rancher could use this to access resources they should no longer have access to. The exposure level will depend on the original permission level granted to the affected project role.

CVE-2021-36775 has a CVSS score of 8.0 (High). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.4.18, 2.5.12, 2.6.3); upgrading removes the vulnerable code path.

Kodem intelligence

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Patched versions include releases 2.4.18, 2.5.12, 2.6.3 and later versions.

1. What is CVE-2021-36775? CVE-2021-36775 is a high-severity security vulnerability in github.com/rancher/rancher (go), affecting versions <= 2.4.17. It is fixed in 2.4.18, 2.5.12, 2.6.3.
2. How severe is CVE-2021-36775? CVE-2021-36775 has a CVSS score of 8.0 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/rancher/rancher are affected by CVE-2021-36775? github.com/rancher/rancher (go) versions <= 2.4.17 is affected.
4. Is there a fix for CVE-2021-36775? Yes. CVE-2021-36775 is fixed in 2.4.18, 2.5.12, 2.6.3. Upgrade to this version or later.
5. Is CVE-2021-36775 exploitable, and should I be worried? Whether CVE-2021-36775 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-36775 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-36775?
   • Upgrade github.com/rancher/rancher to 2.4.18 or later
   • Upgrade github.com/rancher/rancher to 2.5.12 or later
   • Upgrade github.com/rancher/rancher to 2.6.3 or later

Other vulnerabilities in github.com/rancher/rancher