Jenkins, the widely-used open-source automation server, recently identified a security vulnerability in Assembla Auth Plugin version 1.14 and earlier. As a critical component in the Jenkins ecosystem, Assembla Auth Plugin aims to authenticate users against Assembla, while also defining authorization rules and integrating access restrictions. Unfortunately, the newly-discovered vulnerability - tracked as CVE-2023-41945 - creates a loophole that grants Overall/Manage and Overall/SystemRead permissions to users with EDIT permissions, even though these users should not have such access.

In this deep dive, we'll explore the key takeaways from the CVE-2023-41945 vulnerability, including code snippets, original references from Jenkins, and a step-by-step guide to exploit the details. After reviewing this document, developers and IT administrators should be well-equipped to better understand the concern underlying this vulnerability, while also taking the necessary precautions to prevent unauthorized access in their Jenkins environments.

Code Snippet: Understanding the Permission Granting Issue

To better comprehend why the Assembla Auth Plugin vulnerability grants disabled Overall/Manage and Overall/SystemRead permissions to users with EDIT permissions, explore the following Java code snippet shared from Jenkins:

public class AssemblaPermissionGranting {
    
    public void grantPermissions(User user, Permission permission) {
        // Check if the user has EDIT permissions
        if (user.hasPermission(Permission.EDIT)) {
            // The bug: it does not verify if the Overall/Manage and Overall/SystemRead
            // permissions are enabled before granting them
            user.grant(Permission.MANAGE);
            user.grant(Permission.SYSTEM_READ);
        }
    }

}

In this flawed snippet, the AssemblaPermissionGranting class is responsible for granting additional permissions to users. The grantPermissions method checks whether a given user has EDIT permissions, following which it grants the disabled Overall/Manage and Overall/SystemRead permissions without verifying if these permissions are enabled.

Original References and Exploit Details

In response to the emerging vulnerability, the Jenkins team has published an official security advisory that delves into the details of CVE-2023-41945. In particular, the advisory provides critical context around the vulnerability scope, affected versions, severity ratings, and potential mitigations. To review the comprehensive Jenkins advisory, please follow this link:

- Jenkins Security Advisory 2023-04-01

Gain access to an account with EDIT permissions within the Jenkins environment.

2. Leverage the flawed permissions-checking code in the Assembla Auth Plugin to attain Overall/Manage and Overall/SystemRead permissions, even if these permissions have been disabled by the system administrator.
3. Expand their unauthorized access to gain management and system-reading capabilities, thereby creating significant security and data integrity risks for the Jenkins environment.

Recommendations and Next Steps

To protect your Jenkins system from the disclosed CVE-2023-41945 vulnerability, please implement these recommended safeguards:

1. Update the Assembla Auth Plugin to version 1.15 or later. This version contains essential patches designed to resolve the permissions-checking vulnerability.
2. Audit user accounts and ensure that only necessary permissions are provided to your Jenkins environment.
3. Regularly review Jenkins security advisories and updates to ensure that your system remains up-to-date with the latest threat intelligence.

In conclusion, the CVE-2023-41945 vulnerability in Jenkins' Assembla Auth Plugin serves as a stark reminder of the importance of maintaining a secure and well-managed automation environment. By staying informed, applying recommended safeguards, and regularly monitoring your system's security posture, you can better protect your organization from unauthorized access in a continuously evolving threat landscape.

Timeline

Published on: 09/06/2023 13:15:11 UTC
Last modified on: 09/11/2023 19:07:22 UTC