How to remediate – Apache Cassandra CQL Shell Service Detection

1. Introduction

The Apache Cassandra CQL Shell Service Detection identifies instances where the CQL Shell service for Apache Cassandra is running on a remote host. This service allows direct access to the database, potentially exposing it to unauthorized users if not properly secured. Systems commonly affected are servers hosting Apache Cassandra, a distributed NoSQL database. A successful exploit could lead to data breaches, modification of data, or denial of service.

2. Technical Explanation

The CQL Shell service provides an interactive interface for managing and querying the Apache Cassandra database. If left exposed without authentication or access controls, it allows anyone with network access to interact directly with the database. There is no known CVE associated with simply detecting the presence of the shell; however, its existence presents a risk if not secured. An attacker could use the CQL Shell to execute arbitrary queries, potentially leading to data theft or manipulation.

• Root cause: The CQL Shell service is enabled by default and may lack sufficient access controls.
• Exploit mechanism: An attacker connects to the exposed CQL Shell port (typically 9042) and executes malicious queries. For example, an attacker could use a simple query to dump all data from a table.
• Scope: Affected platforms are those running Apache Cassandra versions with the CQL Shell service enabled.

3. Detection and Assessment

Confirming whether a system is vulnerable involves checking for the presence of the CQL Shell service and verifying its configuration. A quick check can identify if the service is listening on the default port, while a thorough method would involve examining the Cassandra configuration files.

• Quick checks: Use netstat -tulnp | grep 9042 to see if anything is listening on port 9042.
• Scanning: Nessus plugin ID 16837 can detect exposed CQL Shell instances as an example only.
• Logs and evidence: Cassandra logs may show connections to the CQL Shell service, but this depends on logging configuration.

netstat -tulnp | grep 9042

4. Solution / Remediation Steps

The primary solution is to restrict access to the CQL Shell service or disable it if not required. These steps aim to minimize exposure and protect the database from unauthorized access.

4.1 Preparation

• Ensure you have appropriate permissions to modify the Cassandra configuration. A roll back plan involves restoring the original configuration files and restarting the service.
• A change window may be required for production systems, with approval from relevant stakeholders.

4.2 Implementation

1. Step 1: Edit the cassandra.yaml file.
2. Step 2: Set native_transport_port: 0 to disable the CQL Shell service. Alternatively, configure authentication and authorization for the service if it must remain enabled.
3. Step 3: Restart the Cassandra service to apply the changes.

4.3 Config or Code Example

Before

native_transport_port: 9042

After

native_transport_port: 0

4.4 Security Practices Relevant to This Vulnerability

List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice. For example: least privilege, input validation, safe defaults, secure headers, patch cadence. If a practice does not apply, do not include it.

• Practice 1: Least privilege – restrict access to the database service to only authorized users and applications.
• Practice 2: Secure Defaults – disable unnecessary services like CQL Shell by default.

4.5 Automation (Optional)

# Example Ansible task to disable CQL Shell
- name: Disable Cassandra CQL Shell
  lineinfile:
    path: /etc/cassandra/cassandra.yaml
    regexp: '^native_transport_port:'
    line: 'native_transport_port: 0'
  notify: Restart Cassandra

5. Verification / Validation

Confirm the fix by checking that the CQL Shell service is no longer listening on port 9042 and verifying that unauthorized access attempts are blocked.

• Post-fix check: Run netstat -tulnp | grep 9042. The output should be empty, indicating the service is not listening.
• Re-test: Re-run the initial detection method (netstat -tulnp | grep 9042) to confirm the service is no longer exposed.
• Smoke test: Verify that applications connecting to Cassandra using authorized credentials can still access the database.
• Monitoring: Monitor Cassandra logs for failed connection attempts on port 9042, which could indicate unauthorized access attempts.

netstat -tulnp | grep 9042

6. Preventive Measures and Monitoring

Suggest only measures that are relevant to the vulnerability type. Use “for example” to keep advice conditional, not prescriptive.

• Baselines: Update your security baseline or policy to include a requirement for disabling unnecessary Cassandra services like CQL Shell.
• Pipelines: Add checks in CI/CD pipelines to ensure that new deployments do not enable the CQL Shell service without proper authentication and authorization.
• Asset and patch process: Implement a regular review cycle for Cassandra configuration files to identify and address potential security vulnerabilities.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Disabling the CQL Shell may impact applications that rely on it for direct database access.
• Risk or side effect 2: Incorrect configuration changes could prevent Cassandra from starting.
• Roll back: Restore the original cassandra.yaml file and restart the Cassandra service.

8. References and Resources

• Vendor advisory or bulletin: https://cassandra.apache.org/