^{CVE-2023-3276:}XML External Entity (XXE) vulnerability in Dromara HuTool up to version 5.8.19 allows attackers to read arbitrary files or perform server-side request forgery.

Overview

The vulnerability in Dromara HuTool's XML parsing functionality allows attackers to exploit XML External Entity (XXE) processing. When the readBySax function in XmlUtil.java processes XML input containing malicious DOCTYPE declarations with external entity references, it can be manipulated to:

• Access files on the filesystem where the application is running
• Make network connections to internal systems
• Cause denial of service conditions through resource exhaustion
• Potentially lead to information disclosure of sensitive data

Applications using HuTool's XML parsing capabilities without additional security controls are at risk. This vulnerability is particularly dangerous because exploit details have been publicly disclosed, lowering the barrier for attackers to leverage this weakness.

Remediation

To address this vulnerability, organizations should:

1. Update to a patched version of HuTool (if available beyond 5.8.19).

2. If updating is not immediately possible, implement one of these mitigations:

   • Disable DTD processing in XML parsers used with HuTool
   • Implement custom XML entity resolution that restricts external entities
   • Use XML parsing alternatives that don't rely on the vulnerable component
   • Apply input validation to reject XML containing DOCTYPE declarations

3. For custom implementations:

   • Set the "javax.xml.parsers.DocumentBuilderFactory" property "http://apache.org/xml/features/disallow-doctype-decl" to true
   • Disable external entity resolution by setting "http://xml.org/sax/features/external-general-entities" and "http://xml.org/sax/features/external-parameter-entities" to false

4. Review application logs for potential exploitation attempts, looking for XML processing errors or unusual file access patterns.

References

1. Original vulnerability disclosure: https://fbdhhhh47.github.io/2023/06/06/hutool-XXE/
2. VulDB entry: https://vuldb.com/?id.231626
3. CWE-611: Improper Restriction of XML External Entity Reference: https://cwe.mitre.org/data/definitions/611.html
4. OWASP XXE Prevention Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html