Introduction

In the realm of web applications, security remains a top priority. XXE (XML External Entity) injection vulnerabilities pose a significant threat, enabling attackers to steal sensitive information or disrupt functionalities. This blog post delves into CVE-2018–8033, an XXE vulnerability impacting Apache OFBiz versions before 16.11.04, which could be exploited for file disclosure. We’ll explore XXE and how to mitigate this specific risk.

What is XXE?

XXE vulnerabilities arise when an XML parser processes external entities within an XML document. These external entities can reference external resources, such as files or URLs. A malicious actor can inject malicious code within the XML data, tricking the parser into fetching and processing unauthorized content.

The Case of Apache OFBiz < 16.11.04 (CVE-2018–8033)

Apache OFBiz, an open-source enterprise resource planning (ERP) software, was susceptible to XXE before version 16.11.04. This vulnerability, assigned CVE-2018–8033, allowed attackers to exploit the application’s HTTP engine to read arbitrary files on the server’s filesystem. By crafting a specially crafted XML payload containing a DOCTYPE declaration referencing an external DTD (Document Type Definition), an attacker could trick the parser into retrieving the DTD, which might contain further malicious instructions to read sensitive files. Imagine an attacker gaining access to critical files like /etc/passwd containing user credentials!

How to Mitigate the Risk

Here’s what you can do to address CVE-2018–8033 and similar XXE vulnerabilities:

• Upgrade: The primary solution is to upgrade Apache OFBiz to version 16.11.04 or later. Upgrading ensures you benefit from the security patches that address this XXE issue.
• Disable External DTD Processing: If immediate upgrade isn’t feasible, consider disabling external DTD processing within your OFBiz configuration. This significantly reduces the attack surface by preventing the parser from fetching external DTDs altogether.
• Input Validation: Implement robust input validation mechanisms to sanitize incoming XML data. This helps prevent the processing of malicious entities by filtering out suspicious elements or attributes.

Proof of Concept (PoC) Exploitation Explanation

Conclusion

XXE vulnerabilities can be severe. By understanding XXE and staying updated with security patches for software like Apache OFBiz, you can significantly improve your application’s security posture. Remember, responsible disclosure practices are vital. If you encounter a vulnerability, report it to the software vendor promptly.

Disclaimer

This blog post is for informational purposes only and should not be used for malicious purposes. Exploit development and vulnerability testing should only be conducted in controlled environments with proper authorization.

Further Resources

• OWASP XXE Prevention Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html
• Apache OFBiz Security: https://ofbiz.apache.org/security.html

Exploit : https://github.com/jamieparfet/Apache-OFBiz-XXE