CVE-2023-40339 - Jenkins Config File Provider Plugin Credentials Leakage Vulnerability

Jenkins is an increasingly popular open-source automation server, allowing users to automate various build, test, and deployment processes. However, like any software, it is not immune to security vulnerabilities. Recently, a significant vulnerability (CVE-2023-40339) was identified in the Jenkins Config File Provider Plugin version 952.va_544a_6234b_46 and earlier.

In this post, we will delve into the details of this vulnerability, presenting a code snippet demonstrating the issue and providing relevant links to original references and exploit details.

Issue Description

The vulnerability resides in the Config File Provider Plugin, a widely-used Jenkins plugin that allows users to manage configuration files as first-class citizens in Jenkins. The plugin makes it easy to maintain these configuration files centrally and use them where needed, as part of a build job.

However, versions 952.va_544a_6234b_46 and earlier of the plugin do not properly mask (i.e., replace with asterisks) sensitive data, such as credentials, specified in configuration files when they are written to the build log. As a result, these credentials become visible in the Jenkins build output, posing a serious security risk.

The issue can be demonstrated with the following example code snippet

// Fetch the credentials using the Config File Provider Plugin
configFileProvider([configFile(fileId: 'jenkins-credentials', targetLocation: 'credentials.txt')]) {
    // Read the credentials from the specified file
    def creds = readFile('credentials.txt').trim()

    // Print the credentials to the build log (should be masked)
    echo "The credentials: ${creds}"
}

Expected output

The credentials: **

Actual output (vulnerable versions)

The credentials: MySecretPassword123

Original References

1. Jenkins Security Advisory: https://www.jenkins.io/security/advisory/2023-04-18/#SECURITY-2699
2. NVD (National Vulnerability Database) Entry: https://nvd.nist.gov/vuln/detail/CVE-2023-40339
3. Config File Provider Plugin - GitHub Repository: https://github.com/jenkinsci/config-file-provider-plugin

Exploit Details

To exploit this vulnerability, an attacker would need access to the Jenkins instance and the ability to view build logs. After gaining access, the attacker can search the build logs for exposed credentials by looking for specific keywords or patterns. With these exposed credentials, the attacker can compromise associated systems or resources, causing severe damage and potentially gaining further unauthorized access to sensitive data.

Mitigation

The Jenkins project has released a security update for the Config File Provider Plugin, addressing this vulnerability. To protect your Jenkins instance and secure sensitive data, it is recommended to upgrade the plugin to version 952.va_544a_6234b_47 or later.

Conclusion

In this long read, we discussed the critical vulnerability CVE-2023-40339, which affects the Config File Provider Plugin in Jenkins. By upgrading the plugin to the latest version, you can help keep your Jenkins instance secure and protect sensitive credentials from being exposed in build logs.

Timeline

Published on: 08/16/2023 15:15:00 UTC
Last modified on: 08/22/2023 18:55:00 UTC