Overview
CVE-2025-66372 describes an XML External Entity (XXE) vulnerability found in Mustang versions prior to 2.16.3. This vulnerability allows a malicious actor to potentially exfiltrate files from the system where the Mustang application is running by crafting a specially designed XML payload. While rated as a low severity issue, understanding and mitigating this risk is crucial for maintaining a secure environment.
Technical Details
XXE vulnerabilities occur when an XML parser processes external entities in a DTD (Document Type Definition) without proper sanitization or input validation. In the case of Mustang, a vulnerable XML parsing routine allows an attacker to define an external entity that points to a local file. When the XML is processed, the content of the specified file is then included in the output, effectively allowing the attacker to read sensitive information. The vulnerability lies in Mustang’s processing of XML data, making it susceptible to attacker-controlled external entities.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) assigns a score of 2.8 to CVE-2025-66372. This score reflects the following characteristics:
- Severity: LOW
- Attack Vector: Network
- Attack Complexity: High
- Privileges Required: None
- User Interaction: Required
- Scope: Unchanged
- Confidentiality Impact: Low
- Integrity Impact: None
- Availability Impact: None
The low severity is primarily due to the high attack complexity and the requirement for user interaction. An attacker needs to craft a malicious XML payload and convince a user to process it for the attack to succeed. The confidentiality impact is limited to the data that can be exfiltrated via the XXE vulnerability.
Possible Impact
While the CVSS score is low, the potential impact of CVE-2025-66372 should not be disregarded. Successful exploitation could allow an attacker to:
- Read configuration files containing sensitive information (e.g., database credentials, API keys).
- Access system files, potentially revealing valuable data about the application’s environment.
- Potentially escalate the attack by leveraging the exfiltrated information to exploit other vulnerabilities.
The actual impact depends on the permissions of the user processing the malicious XML and the sensitivity of the files accessible to that user.
Mitigation or Patch Steps
The recommended mitigation is to upgrade to Mustang version 2.16.3 or later. This version contains a fix that addresses the XXE vulnerability by properly disabling external entity processing or implementing robust input validation.
Specifically:
- Upgrade Mustang: Download and install the latest version of Mustang (2.16.3 or higher) from the official ZUGFeRD project website.
- Verify the Fix: After upgrading, verify that external entity processing is disabled or properly sanitized in the XML parsing routines.
- Input Validation: Review and strengthen input validation procedures for all XML data processed by Mustang.
References
- CVE ID: CVE-2025-66372
- Issue Report: https://github.com/ZUGFeRD/mustangproject/issues/685
- Pull Request (Fix): https://github.com/ZUGFeRD/mustangproject/pull/725
- Release Notes: https://github.com/ZUGFeRD/mustangproject/releases/tag/core-2.16.3
