Summary
Rancher doesn't properly sanitize credentials in cluster template answers
Workarounds
Limit access in Rancher to trusted users. There is not a direct mitigation besides upgrading to the patched Rancher versions.
Important: It is highly advised to review for potential leaked credentials in this scenario, and to change them if deemed necessary.
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.
Impact
It was discovered that in Rancher versions up to and including 2.5.12 and 2.6.3 there is a failure to properly sanitize credentials in cluster template answers. This failure can lead to plaintext storage and exposure of credentials, passwords and API tokens.
The exposed credentials are visible in Rancher to authenticated Cluster Owners, Cluster Members, Project Owners and Project Members on the endpoints /v1/management.cattle.io.clusters, /v3/clusters and /k8s/clusters/local/apis/management.cattle.io/v3/clusters.
Sensitive fields are now stripped from Clusters objects before the object is stored. For objects that existed before this security fix, a one-time migration happens on startup.
Important:
- It is highly advised to review for potential leaked credentials in this scenario, and to change them if deemed necessary.
- The final impact severity for confidentiality, integrity and availability is dependent on the permissions that the leaked credentials have on their own services.
CVE-2021-36783 has a CVSS score of 9.9 (Critical). 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 (2.5.13, 2.6.4); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Patched versions include releases 2.5.13, 2.6.4 and later versions.
Frequently Asked Questions
- What is CVE-2021-36783? CVE-2021-36783 is a critical-severity security vulnerability in github.com/rancher/rancher (go), affecting versions >= 2.5.0, <= 2.5.12. It is fixed in 2.5.13, 2.6.4.
- How severe is CVE-2021-36783? CVE-2021-36783 has a CVSS score of 9.9 (Critical). 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.
- Which versions of github.com/rancher/rancher are affected by CVE-2021-36783? github.com/rancher/rancher (go) versions >= 2.5.0, <= 2.5.12 is affected.
- Is there a fix for CVE-2021-36783? Yes. CVE-2021-36783 is fixed in 2.5.13, 2.6.4. Upgrade to this version or later.
- Is CVE-2021-36783 exploitable, and should I be worried? Whether CVE-2021-36783 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
- What actually determines whether CVE-2021-36783 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.
- How do I fix CVE-2021-36783?
- Upgrade
github.com/rancher/rancherto 2.5.13 or later - Upgrade
github.com/rancher/rancherto 2.6.4 or later
- Upgrade