CVE-2018-6356 Explained : Impact and Mitigation

Jenkins versions prior to 2.107 and Jenkins LTS versions prior to 2.89.4 had a vulnerability that allowed users to bypass base directory restrictions, potentially leading to unauthorized access to files on the Jenkins master.

Understanding CVE-2018-6356

This CVE entry highlights a security vulnerability in Jenkins that could be exploited to download files that users were not authorized to access.

What is CVE-2018-6356?

CVE-2018-6356 is a vulnerability in Jenkins versions before 2.107 and Jenkins LTS versions before 2.89.4 that could be abused to download files from the Jenkins master that users were not supposed to have access to.

The Impact of CVE-2018-6356

The vulnerability could allow users with Overall/Read permission to download files from the Jenkins master, potentially compromising sensitive information.

Technical Details of CVE-2018-6356

This section delves into the technical aspects of the vulnerability.

Vulnerability Description

Jenkins versions before 2.107 and Jenkins LTS before 2.89.4 did not effectively prevent the use of relative paths that could bypass the base directory restriction for URLs accessing plugin resource files.

Affected Systems and Versions

Jenkins versions prior to 2.107
Jenkins LTS versions prior to 2.89.4

Exploitation Mechanism

On Windows, any file accessible to the Jenkins master process could be downloaded.
On other operating systems, any file within the Jenkins home directory accessible to the Jenkins master process could be downloaded.

Mitigation and Prevention

Protecting systems from this vulnerability requires immediate action and long-term security practices.

Immediate Steps to Take

Upgrade Jenkins to version 2.107 or later, or Jenkins LTS to version 2.89.4 or later.
Restrict access permissions to sensitive files and directories.

Long-Term Security Practices

Regularly review and update access controls within Jenkins.
Monitor file downloads and access logs for suspicious activities.

Patching and Updates

Stay informed about security advisories from Jenkins.
Apply patches and updates promptly to address known vulnerabilities.