CVE-2022-23118 – Jenkins Debian Package Builder Plugin Vulnerability: A Deep Dive into the Exploit and How to Stay Safe

CVE-2022-23118 is a critical vulnerability in Jenkins Debian Package Builder Plugin 1.6.11 and earlier versions. The exploit allows agents to invoke command-line git at an attacker-specified path on the controller, which enables attackers to control agent processes and invoke arbitrary OS commands on the controller. In this post, we'll cover the details of this exploit, how it works, and what you should do to safeguard your systems against this vulnerability.

Understanding the Vulnerability

The Jenkins Debian Package Builder Plugin is designed to automate the process of building Debian packages. It provides a user interface for defining the necessary build steps, allowing users to significantly streamline the process. However, it is within this plugin's functionality that the flaw causing this vulnerability lies.

The vulnerability exists due to the capability granted to agents, which can invoke command-line git at an attacker-specified path on the controller. This ability to control the agent processes opens up a dangerous path for attackers, who can exploit this loophole to execute arbitrary OS commands on the controller.

The official Jenkins Security Advisory provides further information on the specifics of this vulnerability: https://www.jenkins.io/security/advisory/2022-02-08/#SECURITY-3173

Exploit Details

To understand the exploit, let's examine a simple code snippet that demonstrates how the vulnerability can be triggered:

// Pseudo-code demonstrating the exploit
AgentInvoke {
  String gitPath = attackerControlledInput(); // Attacker specifies path to 'git'
  CommandLine cmd = Command("git", gitPath);
  cmd.execute(); // Executes the arbitrary 'git' command
}

This pseudo-code example demonstrates the core issue: the gitPath variable receives its value from an attacker-controlled input. By using this input, the attacker can specify a path to a malicious git executable. Consequently, when the plugin invokes the command-line git using the attacker-specified path, it ends up executing arbitrary commands on the controller.

Mitigation Steps

As of February 8th, 2022, the Jenkins project has released a security update addressing the vulnerability in the Debian Package Builder Plugin. It is highly recommended to update to the latest version (1.6.12 or later) to fix the issue. You can find the updated plugin at the following link: https://plugins.jenkins.io/debian-package-builder/

Additionally, it is essential to follow these best practices to ensure the security of your Jenkins environment:

1. Limit the access to Jenkins: Regularly review user permissions and ensure that only trusted individuals have access to the Jenkins environment.
2. Use agent-to-controller security subsystem: Configure it to block agents from executing arbitrary commands on the controller.
3. Update Jenkins and plugins regularly: Ensure that your Jenkins installation and all plugins are up-to-date with the latest patches and security fixes.
4. Employ network-level security: Use firewalls and other network security mechanisms to limit the exposure of your Jenkins environment.

Conclusion

CVE-2022-23118 is a serious vulnerability in the Jenkins Debian Package Builder Plugin, which allows attackers to gain control over agent processes and execute arbitrary OS commands on the controller. While mitigating this vulnerability requires updating the plugin and following best security practices, it highlights the importance of having a proactive approach to application security and regularly patching for discovered vulnerabilities. Stay informed, stay prepared, and keep your Jenkins environment secure.

Timeline

Published on: 01/12/2022 20:15:00 UTC
Last modified on: 01/19/2022 20:25:00 UTC