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Rancher does not automatically clean up a user deleted or disabled from the configured Authentication Provider

High severity GitHub Reviewed Published Jun 17, 2024 in rancher/rancher • Updated Oct 16, 2024

Package

gomod github.com/rancher/rancher (Go)

Affected versions

>= 2.7.0, < 2.7.14
>= 2.8.0, < 2.8.5

Patched versions

2.7.14
2.8.5

Description

Impact

A vulnerability has been identified in which Rancher does not automatically clean up a user which has been deleted from the configured authentication provider (AP). This characteristic also applies to disabled or revoked users, Rancher will not reflect these modifications which may leave the user’s tokens still usable.

An AP must be enabled to be affected by this, as the built-in User Management feature is not affected by this vulnerability.
This issue may lead to an adversary gaining unauthorized access, as the user’s access privileges may still be active within Rancher even though they are no longer valid on the configured AP (please consult the MITRE ATT&CK - Technique - Valid Accounts for further information about the associated technique of attack).

It’s important to note that all configurable APs are impacted, see Rancher Docs - Configuring Authentication - External vs. Local Authentication to get the full authentication providers list.

To address this issue, the fix introduces a new user retention process that can be configured to run periodically and disable and/or delete inactive users. If enabled a user becomes subject to retention if they don't login for a configurable period of time. It's possible to set overrides for users that are used mainly for programmatic access (e.g. CI, scripts etc.) so that they don't become subject to retention for a longer period of time or at all. The user retention process is disabled by default, to avoid deleting wrong accounts. It is up to each user to enable it and configure the retention period as it best suits its environment.

Be aware that once the process is enabled, it might take a few days for previous users that have been revoked or deleted from the AP to be automatically removed from Rancher. To attenuate the risk of this condition, we recommend to regularly audit the AP’s user accounts for activity and manually deactivate or remove them from Rancher, if they are no longer needed.

For further information about the user retention process configuration, please refer to the dedicated documentation Rancher Docs - Advanced User Guides - Enable User Retention.

Patches

Patched versions include releases 2.7.14 and 2.8.5.

Workarounds

Administrators that are unable to update to a patched Rancher Manager version, are advised to delete Rancher users, via kubectl or through the UI, as soon as those users are deleted from the Authentication Provider. If a user needs to be temporarily disabled on the Authentication Provider, similar intervention will need to take place to reflect that change on Rancher Manager.

Below is a procedure to list and remove a deleted/disabled user in Rancher using kubectl (with a privileged kubeconfig).

  1. List all users bound to a supported external auth provider, then returns username, uid, displayName and PrincipalIds which contains the related authprovider_user://ID
#!/bin/bash

for authprovider in {activedirectory,azure,common,genericoidc,github googleauth, keycloakoidc,ldap,oidc,publicapi,saml}
do 
	kubectl get users -o json | jq --arg authprovider "$authprovider" '.items[] | select(.principalIds[] | test("^" + $authprovider + "_user://")) | {username: .metadata.name, uid: .metadata.uid, displayName: .displayName, principalIds: .principalIds}'
done
  1. Once the authprovider_user://ID (and/or DisplayName) is confirmed, remove the user from the Rancher UI or using kubectl delete users <USERNAME>.

For more information

If you have any questions or comments about this advisory:

References

@pdellamore pdellamore published to rancher/rancher Jun 17, 2024
Published to the GitHub Advisory Database Jun 17, 2024
Reviewed Jun 17, 2024
Published by the National Vulnerability Database Oct 16, 2024
Last updated Oct 16, 2024

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

EPSS score

0.043%
(11th percentile)

Weaknesses

CVE ID

CVE-2023-22650

GHSA ID

GHSA-9ghh-mmcq-8phc

Source code

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