CVE-2021-4200

Write access to the catalog for any user when restricted-admin role is enabled in Rancher

Workarounds

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

Note: If you use the restricted-admin as the default admin role in your environment, it's highly advised to review CatalogTemplates and CatalogTemplateVersions for possible malicious modifications.

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 the restricted-admin role in Rancher. For this role to be active, Rancher must be bootstrapped with the environment variable CATTLE_RESTRICTED_DEFAULT_ADMIN=true or the configuration flag restrictedAdmin=true.

A flaw was discovered in Rancher versions from 2.5.0 up to and including 2.5.12 and from 2.6.0 up to and including 2.6.3 where the global-data role in cattle-global-data namespace grants write access to the Catalogs. Since each user with any level of catalog access was bound to the global-data role, this grants write access to templates (CatalogTemplates) and template versions (CatalogTemplateVersions) for any user with any level of catalog access. New users created in Rancher are by default assigned to the user role (standard user), which is not designed to grant write catalog access. This vulnerability effectively elevates the privilege of any user to write access for the catalog template and catalog template version resources.

A malicious user could abuse this vulnerability to:

1. Make applications or individual versions of applications visible or hidden on the UI, by modifying version and rancherMaxVersion fields.
2. Change the logo (field icon) of an application or template to an arbitrary image.
3. Make a chart appear as a trusted or partner chart. This can be abused to make less trusted charts, such as customer defined charts, appear more legitimate than they are, by adding the label io.rancher.certified: partner.
4. Swap template versions between templates of charts inside the same catalog. This can be exploited to swap the files from one chart or version to another, by changing versionDir field. When a user on the target cluster deploys their chart, it will deploy the modified version.

This vulnerability does not allow to modify the base64 encoded files fields of the templateVersions, so one cannot inject arbitrary data to charts that have already been pulled from their respective catalog.

Without access to the Catalog, malicious users are limited to injecting apps which already exist in a registered catalog. They would need write access to the catalog or external write access to a source repo to inject arbitrary code.

The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access. Typical impact: privilege escalation beyond the intended level.

CVE-2021-4200 has a CVSS score of 8.1 (High). The vector is network-reachable, low privileges required, and no user interaction. 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 (2.6.4, 2.5.13); upgrading removes the vulnerable code path.

Kodem intelligence

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Patched versions include releases 2.5.13, 2.6.4 and later versions.

1. What is CVE-2021-4200? CVE-2021-4200 is a high-severity improper privilege management vulnerability in github.com/rancher/rancher (go), affecting versions >= 2.6.0, < 2.6.4. It is fixed in 2.6.4, 2.5.13. The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access.
2. How severe is CVE-2021-4200? CVE-2021-4200 has a CVSS score of 8.1 (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-2021-4200? github.com/rancher/rancher (go) versions >= 2.6.0, < 2.6.4 is affected.
4. Is there a fix for CVE-2021-4200? Yes. CVE-2021-4200 is fixed in 2.6.4, 2.5.13. Upgrade to this version or later.
5. Is CVE-2021-4200 exploitable, and should I be worried? Whether CVE-2021-4200 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-2021-4200 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-2021-4200?
   • Upgrade github.com/rancher/rancher to 2.6.4 or later
   • Upgrade github.com/rancher/rancher to 2.5.13 or later

Other vulnerabilities in github.com/rancher/rancher