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Bypass of node policy download ACL

High
amousset published GHSA-x92w-5577-fr2c Jan 24, 2026

Package

rudder-server (rudder)

Affected versions

< 9.0.1, >= 9.0.0
< 8.3.6

Patched versions

9.0.1
8.3.6
rudder-server-root (rudder)
>= 4.2.0
None

Description

Impact

An accepted node could download the policies of other nodes (when knowing their Rudder node id) managed by the same server or relay. This bug is present since Rudder 4.2. Policies should not contain secrets but can still contain sensitive information about the applied configuration.

In particular, when having relays, it is possible to enumerate other nodes managed from the relay by fetching the relay's policies.

Exploitation logs

You can check the server's and relay's Apache httpd logs for exploitation traces using this script:

Checking /var/log/rudder/apache2/access.log
Found  line, node 222f83f2-502c-4bc8-9039-0aeb7ad487e6 downloading policies for 23952265-30bc-4d15-83f4-dc22ac045878:
  > 192.168.215.131 - 222f83f2-502c-4bc8-9039-0aeb7ad487e6 [30/Oct/2025:01:43:46 +0100] "GET /policies/23952265-30bc-4d15-83f4-dc22ac045878/rules/rudder.tar.bz2 HTTP/1.1" 200 87866 "-" "curl/7.88.1"
Found suspicious line, node 222f83f2-502c-4bc8-9039-0aeb7ad487e6 downloading policies for 23952265-30bc-4d15-83f4-dc22ac045878:
  > 192.168.215.131 - 222f83f2-502c-4bc8-9039-0aeb7ad487e6 [30/Oct/2025:08:32:15 +0100] "GET /policies/23952265-30bc-4d15-83f4-dc22ac045878/rules/rudder.tar.bz2 HTTP/1.1" 200 87866 "-" "curl/7.88.1"
Found suspicious line, node 222f83f2-502c-4bc8-9039-0aeb7ad487e6 downloading policies for 23952265-30bc-4d15-83f4-dc22ac045878:
  > 192.168.215.131 - 222f83f2-502c-4bc8-9039-0aeb7ad487e6 [30/Oct/2025:08:33:02 +0100] "GET /policies/23952265-30bc-4d15-83f4-dc22ac045878/rules/cfengine-community/run_interval HTTP/1.1" 200 2111 "-" "curl/7.88.1"
Checking /var/log/rudder/apache2/access.log.1
Checking /var/log/rudder/apache2/access.log.10.gz

Workarounds

Replace the affected configuration file with the patched version on all the servers and relays. It will be automatically updated on the next Rudder upgrade, there is nothing to do.

For Rudder 8.3 (& 8.2)

On all Rudder 8.3 servers and relays:

  • put the patched rudder-apache-relay-ssl.conf into /opt/rudder/etc/rudder-apache-relay-ssl.conf
  • restart the apache2/httpd service to apply the change

Note: Rudder 8.2 is now unmaintained, but the patch works as well.

For Rudder 9.0

On all Rudder 9.0 servers and relays:

  • put the patched rudder-apache-relay-ssl.conf.j2 into /opt/rudder/etc/rudder-apache-relay-ssl.conf.j2
  • run the agent with rudder agent run to apply the change

Cause

The problem comes from an incorrect ACL in the HTTPS policy download configuration. The configuration files are served from /var/rudder/share/{node_id}/, and its access is controlled by a RewriteRule which redirects the URL to the actual files when the ID in the certificate (that needs to be accepted in the inventory) matches the required policies:

RewriteCond "%{SSL:SSL_CLIENT_S_DN_UID}=$1" "^(.*?)=\1"
RewriteRule /policies/(.*?)/(.*) /var/rudder/share/$1/$2

As the policies are lacking a SSLVerifyClient at the virtual host level, the client certificate is not read and SSL_CLIENT_S_DN_UID is always empty. And due to a missing $ anchor in the regex, the RewriteCond guarding the access is defined when the variable is empty, leading to a bypass of the ACL:

[Wed Oct 29 22:11:18.072897 2025] [rewrite:trace4] [pid 64704:tid 64722] mod_rewrite.c(4305): [client 192.168.2.3:59478] 192.168.2.3 - - [server/sid#7f5c26168a08][rid#7f5c242290a0/initial] RewriteCond: input='=18c3a1a6-2dad-40eb-a1dd-2fb04a070d94' pattern='^(.*?)=\\1' => matched

The policies directory configuration has a SSLVerifyClient require option, but it comes too late and only enforces the validity of the certificate against the list of accepted nodes. This means that the only applied controls are the allowed networks restrictions and the validity of the certificate (which makes the download only possible with an accepted node's key & certificate).

Patches

References

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

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:A/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:H

CVE ID

No known CVE

Weaknesses

Improper Certificate Validation

The product does not validate, or incorrectly validates, a certificate. Learn more on MITRE.

Permissive Regular Expression

The product uses a regular expression that does not sufficiently restrict the set of allowed values. Learn more on MITRE.