End of life: 5/4/2027, Latest version: 7.1.8

Reflected Cross-Site Scripting (XSS) vulnerability in the Graylog Web Interface console, version 2.2.3, caused by a lack of proper sanitization and escaping in HTML output. Several endpoints include segments of the URL directly in the response without applying output encoding, allowing an attacker to inject and execute arbitrary JavaScript code when a user visits a specially crafted URL. Exploitation of this vulnerability may allow script execution in the victim's browser and limited manipulation of the affected user's session context, through the  '/system/indexsets/' endpoint.

Reflected Cross-Site Scripting (XSS) vulnerability in the Graylog Web Interface console, version 2.2.3, caused by a lack of proper sanitization and escaping in HTML output. Several endpoints include segments of the URL directly in the response without applying output encoding, allowing an attacker to inject and execute arbitrary JavaScript code when a user visits a specially crafted URL. Exploitation of this vulnerability may allow script execution in the victim's browser and limited manipulation of the affected user's session context, through the  '/system/pipelines/' endpoint.

Reflected Cross-Site Scripting (XSS) vulnerability in the Graylog Web Interface console, version 2.2.3, caused by a lack of proper sanitization and escaping in HTML output. Several endpoints include segments of the URL directly in the response without applying output encoding, allowing an attacker to inject and execute arbitrary JavaScript code when a user visits a specially crafted URL. Exploitation of this vulnerability may allow script execution in the victim's browser and limited manipulation of the affected user's session context, through the  '/

alerts

/' endpoint.

Reflected Cross-Site Scripting (XSS) vulnerability in the Graylog Web Interface console, version 2.2.3, caused by a lack of proper sanitization and escaping in HTML output. Several endpoints include segments of the URL directly in the response without applying output encoding, allowing an attacker to inject and execute arbitrary JavaScript code when a user visits a specially crafted URL. Exploitation of this vulnerability may allow script execution in the victim's browser and limited manipulation of the affected user's session context, through the  '/system/nodes/' endpoint.

Reflected Cross-Site Scripting (XSS) vulnerability in the Graylog Web Interface console, version 2.2.3, caused by a lack of proper sanitization and escaping in HTML output. Several endpoints include segments of the URL directly in the response without applying output encoding, allowing an attacker to inject and execute arbitrary JavaScript code when a user visits a specially crafted URL. Exploitation of this vulnerability may allow script execution in the victim's browser and limited manipulation of the affected user's session context, through the '/system/authentication/users/edit/' endpoint.

Improper Access Control (IDOR) in the Graylog API, version 2.2.3, which occurs when modifying the user ID in the URL. An authenticated user can access other user's profiles without proper authorization checks. Exploiting this vulnerability allows valid users of the system to be listed and sensitive third-party information to be accessed, such as names, email addresses, internal identifiers, and last activity. The endpoint 'http://<IP>:12900/users/<myuser>' does not implement object-level authorization validations.

Not properly invalidated session vulnerability in Graylog Web Interface, version 2.2.3, due to incorrect management of session invalidation after new logins. The application generates a new 'sessionId' each time a user authenticates, but does not invalidate previously issued session identifiers, which remain valid even after multiple consecutive logins by the same user. As a result, a stolen or leaked 'sessionId' can continue to be used to authenticate valid requests. Exploiting this vulnerability would allow an attacker with access to the web service/API network (port 9000 or HTTP/S endpoint of the server) to reuse an old session token to gain unauthorized access to the application, interact with the API/web, and compromise the integrity of the affected account.

End of life: 11/3/2026, Latest version: 7.0.12

End of life: 6/30/2026, Latest version: 6.3.15

End of life: 4/28/2026, Latest version: 6.2.14

Summary

Arbitrary classes can be loaded and instantiated using a HTTP PUT request to the /api/system/clusterconfig/ endpoint.

Details

Graylog's cluster config system uses fully qualified class names as config keys. To validate the existence of the requested class before using them, Graylog loads the class using the class loader.

https://github.com/Graylog2/graylog2-server/blob/e458db8bf4f789d4d19f1b37f0263f910c8d036c/graylog2-server/src/main/java/org/graylog2/rest/resources/system/ClusterConfigResource.java#L208-L214

PoC A request of the following form will output the content of the /etc/passwd file:

curl -u admin:<admin-password> -X PUT http://localhost:9000/api/system/clusterconfig/java.io.File \ -H "Content-Type: application/json" \ -H "X-Requested-By: poc" \ -d '"/etc/passwd"'

To perform the request, authorization is required. Only users posessing the clusterconfigentry:create and clusterconfigentry:edit permissions are allowed to do so. These permissions are usually only granted to Admin users.

Impact

If a user with the appropriate permissions performs the request, arbitrary classes with 1-arg String constructors can be instantiated.

This will execute arbitrary code that is run during class instantiation.

In the specific use case of java.io.File, the behaviour of the internal web-server stack will lead to information exposure by including the entire file content in the response to the REST request.

Credits

Analysis provided by Fabian Yamaguchi - Whirly Labs (Pty) Ltd

Impact Reauthenticating with an existing session cookie would re-use that session id, even if for different user credentials. In this case, the pre-existing session could be used to gain elevated access to an existing Graylog login session, provided the malicious user could successfully inject their session cookie into someone else's browser.

The complexity of such an attack is high, because it requires presenting a spoofed login screen and injection of a session cookie into an existing browser, potentially through an XSS attack. No such attack has been discovered.

Patches Graylog 5.1.11 and 5.2.4, and any versions of the 6.0 development branch contain patches to not re-use sessions under any circumstances, making this type of attack impossible.

Workarounds Using short session expiration and explicit log outs of unused sessions can help limiting the attack vector. Unpatched this vulnerability exists, but is relatively hard to exploit. A proxy could be leveraged to clear the authentication cookie for the Graylog server URL for the /api/system/sessions endpoint, as that is the only one vulnerable.

Analysis provided by Fabian Yamaguchi - Whirly Labs (Pty) Ltd

A Session ID leak in the DEBUG log file in Graylog before 4.1.2 allows attackers to escalate privileges (to the access level of the leaked session ID).

A Session ID leak in the audit log in Graylog before 4.1.2 allows attackers to escalate privileges (to the access level of the leaked session ID).