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Rancher's External RoleTemplates can lead to privilege escalation

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 whereby privilege escalation checks are not properly enforced for RoleTemplateobjects when external=true, which in specific scenarios can lead to privilege escalation.

The bug in the webhook rule resolver ignores rules from a ClusterRole for external RoleTemplates when its context is set to either project or is left empty. The fix introduces a new field to the RoleTemplate CRD named ExternalRules. The new field will be used to resolve rules directly from the RoleTemplate. Additionally, rules from the backing ClusterRole will be used if ExternalRules is not provided. The new field will always take precedence when it is set, and serve as the source of truth for rules used when creating Rancher resources on the local cluster.

Please note that this is a breaking change for external RoleTemplates, when context is set to project or empty and the backing ClusterRole does not exist, as this was not previously required.

Important: The fix is automatically applied when upgrading to the release lines 2.8and above. For users still on the 2.7 release line, after the upgrade to a patched version, users are required to opt-in to the fix by enabling the external-rules feature flag.

Please consult the associated MITRE ATT&CK - Technique - Exploitation for Privilege Escalation for further information about this category of attack.

Patches

Patched versions include releases 2.7.14 and 2.8.5.

Workarounds

The following script was developed for Rancher Manager administrators to identify RoleTemplates impacted by this vulnerability. The script requires jq installed and a kubeconfig with access to Rancher local cluster; it can also be executed in Rancher's kubectl shell.

#!/bin/bash
set -euo pipefail

# get all RoleTemplates with .context == "project" or .context == "" that don't have externalRules.
rts=$(kubectl get roletemplates -o json | jq -r  '.items[] | select((.context == "project" or .context == "") and .external == true and .externalRules == null and .builtin == false) | .metadata.name')
found_invalid_rt=false

for rt in $rts; do
  if ! kubectl get clusterrole "$rt" > /dev/null 2>&1; then
     echo "$rt" # prints RoleTemplate names that don't have a backing ClusterRole
     found_invalid_rt=true
  fi
done

if ! $found_invalid_rt ; then
    echo 'This cluster is not affected by CVE-2023-32197: no RoleTemplate objects found'
fi

It will return all objects affected by this vulnerability. The administrator can fix those objects by creating the backing ClusterRole that they refer to.

References

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 High
Attack Requirements None
Privileges Required High
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:H/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

EPSS score

0.043%
(11th percentile)

Weaknesses

CVE ID

CVE-2023-32196

GHSA ID

GHSA-64jq-m7rq-768h

Source code

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