CVE-2017-1000386 Explained : Impact and Mitigation

In earlier versions, the Jenkins Active Choices plugin (version 1.5.3 and earlier) had a vulnerability that allowed users with Job/Configure permission to add custom HTML to the 'Build With Parameters' page using the 'Active Choices Reactive Reference Parameter' type. This HTML could potentially include JavaScript code. To address this, the plugin now sanitizes any HTML content added to the 'Build With Parameters' page, but only if the script is executed inside a sandbox. Unsandboxed scripts, which require administrator approval, are subject to the administrator's decision to allow or disallow potentially problematic script output.

Understanding CVE-2017-1000386

This section provides insights into the nature and impact of the CVE.

What is CVE-2017-1000386?

CVE-2017-1000386 is a vulnerability found in the Jenkins Active Choices plugin, specifically affecting versions 1.5.3 and earlier. It allowed users with specific permissions to inject custom HTML, potentially including malicious JavaScript, into certain pages.

The Impact of CVE-2017-1000386

The vulnerability in the Jenkins Active Choices plugin could have allowed malicious users to execute arbitrary JavaScript code, posing a security risk to the affected systems. By exploiting this flaw, attackers could potentially manipulate the 'Build With Parameters' page and compromise the integrity of the Jenkins environment.

Technical Details of CVE-2017-1000386

This section delves into the technical aspects of the CVE.

Vulnerability Description

The Jenkins Active Choices plugin version 1.5.3 and earlier allowed users with Job/Configure permission to provide arbitrary HTML on the 'Build With Parameters' page through the 'Active Choices Reactive Reference Parameter' type. This could include arbitrary JavaScript. Active Choices now sanitizes the HTML inserted on the 'Build With Parameters' page if and only if the script is executed in a sandbox. As unsandboxed scripts are subject to administrator approval, it is up to the administrator to allow or disallow problematic script output.

Affected Systems and Versions

Product: Not applicable
Vendor: Not applicable
Versions affected: Version 1.5.3 and earlier

Exploitation Mechanism

The vulnerability allowed users with Job/Configure permission to inject custom HTML, potentially containing malicious JavaScript, into the 'Build With Parameters' page using the 'Active Choices Reactive Reference Parameter' type. The execution of unsandboxed scripts required administrator approval.

Mitigation and Prevention

This section outlines steps to mitigate and prevent the exploitation of CVE-2017-1000386.

Immediate Steps to Take

Update the Jenkins Active Choices plugin to the latest version that addresses the vulnerability.
Restrict Job/Configure permissions to trusted users only.
Regularly monitor and review custom HTML content added to the 'Build With Parameters' page.

Long-Term Security Practices

Implement a least privilege model for user permissions within Jenkins.
Educate users on the risks associated with injecting custom HTML and JavaScript.
Conduct periodic security audits and vulnerability assessments of Jenkins plugins.

Patching and Updates

Ensure timely installation of security patches and updates for Jenkins and its associated plugins to address known vulnerabilities.