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GHSA-p6gg-5hf4-4rgj
No affected components available
Summary
Arbitrary classes can be loaded and instantiated using a HTTP PUT request to the /api/system/cluster_config/ 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/cluster_config/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
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. 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 high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is moderate. The vulnerability is likely 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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