How to remediate – Prometheus Sensitive Endpoint Detected

1. Introduction

Prometheus Sensitive Endpoint Detected refers to a publicly accessible endpoint on a Prometheus monitoring server. Prometheus is designed to record metrics, but exposing these endpoints without protection allows attackers to gather information about your application environment. This could lead to further attacks targeting specific services or data. A successful exploit can compromise confidentiality of system details and potentially availability if attacker actions disrupt monitoring.

2. Technical Explanation

The root cause is typically an insecure configuration that does not require authentication for access to Prometheus endpoints. Attackers can then directly query these endpoints using PromQL to understand the internal workings of monitored applications. An example exploit involves querying the endpoint to identify running services, their versions, and potentially sensitive data exposed as metrics. This vulnerability affects systems running publicly accessible Prometheus instances.

• Root cause: missing or weak authentication on Prometheus endpoints.
• Exploit mechanism: an attacker sends HTTP requests to the Prometheus endpoint to retrieve metrics data without needing credentials. For example, querying `/metrics` directly via a web browser or `curl`.
• Scope: Affected platforms include any operating system running a publicly exposed Prometheus server (Linux, Windows, macOS).

3. Detection and Assessment

Confirming vulnerability involves checking if the endpoint is accessible without authentication. A quick check can verify basic accessibility, while thorough methods involve examining configuration files.

• Quick checks: Use `curl` or a web browser to access the `/metrics` endpoint of your Prometheus server. If data is returned without prompting for credentials, it’s likely vulnerable.
• Scanning: Nessus plugin ID 16827 can identify exposed Prometheus instances. This is an example only and may require tuning.
• Logs and evidence: Examine web server logs (e.g., Apache or Nginx) for requests to the `/metrics` endpoint from unknown sources.

curl http://your-prometheus-server/metrics

4. Solution / Remediation Steps

The solution involves securing access to the Prometheus endpoint by requiring authentication or restricting access via IP filtering.

4.1 Preparation

• Ensure you have access credentials available and understand the impact of blocking external access. Roll back involves restoring the original configuration file and restarting the service.
• A change window may be needed depending on service criticality, requiring approval from system owners.

4.2 Implementation

1. Step 1: Configure authentication using a method like basic authentication or OAuth2. Edit your `prometheus.yml` file to enable authentication.
2. Step 2: Restart the Prometheus service for the changes to take effect.
3. Step 3: If authentication is not feasible, implement IP source filtering to restrict access only to trusted networks using firewall rules.

4.3 Config or Code Example

Before

# prometheus.yml (no authentication)
global:
  scrape_interval: 15s
scrape_configs:
  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']

After

# prometheus.yml (basic authentication)
global:
  scrape_interval: 15s
  http_auth_username: 'your_username'
  http_auth_password: 'your_password'
scrape_configs:
  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']

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.

• Least privilege: limit access to Prometheus endpoints only to authorized users or systems.
• Secure Defaults: configure authentication by default instead of relying on open access.

4.5 Automation (Optional)

# Example Ansible task to update prometheus.yml with authentication details
- name: Configure Prometheus Authentication
  copy:
    src: prometheus.yml.j2
    dest: /etc/prometheus/prometheus.yml
    owner: prometheus
    group: prometheus
    mode: 0640
  notify: Restart Prometheus

5. Verification / Validation

• Post-fix check: Attempt to access `/metrics` via `curl`. You should receive a 401 Unauthorized error, indicating authentication is now required.
• Re-test: Repeat the initial curl command from the Detection section. The endpoint should no longer return data without credentials.
• Monitoring: Monitor web server logs for failed authentication attempts to identify potential unauthorized access attempts.

curl http://your-prometheus-server/metrics

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 to include a requirement for authentication on all publicly accessible monitoring endpoints.
• Asset and patch process: Regularly review the configuration of Prometheus instances as part of your asset management process.

7. Risks, Side Effects, and Roll Back

• Roll back: Restore the original `prometheus.yml` file from backup and restart the Prometheus service.

8. References and Resources

• Vendor advisory or bulletin: https://prometheus.io/
• NVD or CVE entry: No specific CVE is associated with a generally exposed endpoint, but related CWEs are listed below.
• Product or platform documentation relevant to the fix: https://prometheus.io/docs/instrumenting/exporters/