CVE-2017-12621 Explained : Impact and Mitigation

Apache Commons Jelly XML External Entity (XXE) Vulnerability

Understanding CVE-2017-12621

Apache Commons Jelly prior to version 1.0.1 is vulnerable to XML External Entity (XXE) attacks when parsing Jelly files.

What is CVE-2017-12621?

CVE-2017-12621 is a vulnerability in Apache Commons Jelly that arises when a custom doctype entity with a "SYSTEM" entity and URL is declared in a Jelly file. This vulnerability allows for potential XXE attacks.

The Impact of CVE-2017-12621

The vulnerability in Apache Commons Jelly could lead to information disclosure through XXE attacks, compromising the security and integrity of systems utilizing affected versions.

Technical Details of CVE-2017-12621

Apache Commons Jelly Vulnerability

Vulnerability Description

When parsing Jelly files using Apache Xerces, if a custom doctype entity with a URL is declared and used in the file's body, the parser will connect to the specified URL, creating an opportunity for XXE attacks.

Affected Systems and Versions

Product: Apache Commons Jelly
Vendor: Apache Software Foundation
Versions Affected: 1.0

Exploitation Mechanism

The vulnerability is exploited by declaring a custom doctype entity with a "SYSTEM" entity and URL in a Jelly file, triggering a connection to the specified URL during parser instantiation.

Mitigation and Prevention

Protecting Against CVE-2017-12621

Immediate Steps to Take

Update Apache Commons Jelly to version 1.0.1 or later to mitigate the vulnerability.
Avoid using custom doctype entities with URLs in Jelly files to prevent XXE attacks.

Long-Term Security Practices

Regularly monitor security advisories and updates from Apache Software Foundation.
Implement secure coding practices to prevent XML-related vulnerabilities.

Patching and Updates

Apply patches and updates provided by Apache Software Foundation to address security issues and vulnerabilities in Apache Commons Jelly.