Summary
Rancher does not Properly Validate Account Bindings in SAML Authentication Enables User Impersonation on First Login
Workarounds
Rancher deployments that can't upgrade, could temporarily disable the SAML-based AP as a temporary workaround. However, upgrading is recommended.
References
If you have any questions or comments about this advisory:
- Reach out to the SUSE Rancher Security team for security related inquiries.
- Open an issue in the Rancher repository.
- Verify with our support matrix and product support lifecycle.
Impact
A vulnerability in Rancher has been discovered, leading to a local user impersonation through SAML Authentication on first login.
The issue occurs when a SAML authentication provider (AP) is configured (e.g. Keycloak). A newly created AP user can impersonate any user on Rancher by manipulating cookie values during their initial login to Rancher. This vulnerability could also be exploited if a Rancher user (present on the AP) is removed, either manually or automatically via the User Retention feature with delete-inactive-user-after.
More precisely, Rancher validates only a subset of input from the SAML assertion request; however, it trusts and uses values that are not properly validated. An attacker could then configure the saml_Rancher_UserID cookie and the saml_Rancher_Action cookie so that the user principal from the AP will be added to the user specified by the attacker (from saml_Rancher_UserID). Rancher can then be deceived by setting saml_Rancher_UserID to the admin's user ID and saml_Rancher_Action to testAndEnable, thereby executing the vulnerable code path and leading to privilege escalation.
Note that the vulnerability impacts all SAML APs available in Rancher. However the following Rancher deployments are not affected:
- Rancher deployments not using SAML-based AP.
- Rancher deployments using SAML-based AP, where all SAML users are already signed in and linked to a Rancher account.
Please consult the associated MITRE ATT&CK - Technique - Access Token Manipulation: Token Impersonation/Theft for further information about this category of attack.
The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.
CVE-2025-23389 has a CVSS score of 8.4 (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 (2.8.13, 2.9.7, 2.10.3); 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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This vulnerability is addressed by adding the UserID claim to a JWT signed token, which is protected against tampering.
Patched versions include releases v2.8.13, v2.9.7 and v2.10.3.
Frequently Asked Questions
- What is CVE-2025-23389? CVE-2025-23389 is a high-severity improper authentication vulnerability in github.com/rancher/rancher (go), affecting versions >= 2.8.0, < 2.8.13. It is fixed in 2.8.13, 2.9.7, 2.10.3. The application does not adequately verify the identity of a user, device, or process before granting access.
- How severe is CVE-2025-23389? CVE-2025-23389 has a CVSS score of 8.4 (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.
- Which versions of github.com/rancher/rancher are affected by CVE-2025-23389? github.com/rancher/rancher (go) versions >= 2.8.0, < 2.8.13 is affected.
- Is there a fix for CVE-2025-23389? Yes. CVE-2025-23389 is fixed in 2.8.13, 2.9.7, 2.10.3. Upgrade to this version or later.
- Is CVE-2025-23389 exploitable, and should I be worried? Whether CVE-2025-23389 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-2025-23389 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-2025-23389?
- Upgrade
github.com/rancher/rancherto 2.8.13 or later - Upgrade
github.com/rancher/rancherto 2.9.7 or later - Upgrade
github.com/rancher/rancherto 2.10.3 or later
- Upgrade