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GHSA-mq23-vvg7-xfm4
No affected components available
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.
Patches
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.
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.
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a low impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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