CVE-2025-31497: TEIGarage XXE Injection Vulnerability

CVE-2025-31497 Overview

TEIGarage, a webservice and RESTful service designed to transform, convert, and validate various document formats with a focus on the TEI (Text Encoding Initiative) format, contains a critical XML External Entity (XXE) Injection vulnerability in its document conversion functionality. The service processes XML files during conversion operations but fails to disable external entity processing, allowing attackers to read arbitrary files from the server's filesystem.

Critical Impact

Attackers can exploit this XXE vulnerability to read sensitive files from the server's filesystem, potentially exposing configuration files, credentials, and other confidential information. Additionally, this vulnerability may enable Server-Side Request Forgery (SSRF) attacks against internal services depending on server configuration.

Affected Products

• TEIGarage versions prior to 1.2.4
• TEIGarage document conversion service endpoints
• Systems utilizing TEIGarage for XML/TEI format transformations

Discovery Timeline

• 2025-04-15 - CVE-2025-31497 published to NVD
• 2025-04-16 - Last updated in NVD database

Technical Details for CVE-2025-31497

Vulnerability Analysis

This XML External Entity (XXE) Injection vulnerability (CWE-611) exists within TEIGarage's document conversion functionality. The core issue stems from the service's failure to properly configure the XML parser with secure processing features when handling user-supplied XML documents during format conversion operations.

When TEIGarage processes an XML document for conversion, the underlying XML parser accepts and resolves external entity declarations by default. An attacker can craft a malicious XML document containing external entity references that point to local file system paths or internal network resources. When the parser processes these entities, it retrieves the referenced content and includes it in the processing context.

The vulnerability enables complete read access to any file readable by the web service process, which typically includes application configuration files, environment variables, and potentially database credentials. The network-accessible nature of the service combined with no authentication requirements significantly increases the exploitability window.

Root Cause

The root cause of this vulnerability is the absence of secure XML parsing configuration in TEIGarage's document processing pipeline. The XML parser is instantiated without explicitly disabling external entity resolution features such as XMLConstants.FEATURE_SECURE_PROCESSING. This default-insecure configuration allows the parser to resolve both local file references and external URL references embedded in DOCTYPE declarations and entity definitions within user-supplied XML documents.

Attack Vector

The attack vector is network-based, requiring no authentication or user interaction. An attacker can submit a specially crafted XML document to TEIGarage's conversion endpoint containing malicious external entity declarations. The entity definitions typically reference sensitive local files using file:// protocol handlers or internal services using http:// handlers.

When the XML parser encounters these entity references during the conversion process, it resolves them by fetching the referenced content. The attacker can then retrieve this content through the conversion response or error messages, effectively exfiltrating sensitive server-side data. The attack surface includes any TEIGarage endpoint that accepts XML input for format transformation or validation.

Detection Methods for CVE-2025-31497

Indicators of Compromise

• Unusual XML conversion requests containing DOCTYPE declarations with ENTITY definitions referencing local file paths (e.g., /etc/passwd, /etc/shadow, application configuration files)
• HTTP requests to conversion endpoints with XML payloads containing file://, http://, or other protocol handlers in entity declarations
• Unexpected outbound connections from the TEIGarage service to internal network addresses or localhost services
• Application logs showing attempts to access files outside the expected document processing directories

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect and block XML payloads containing DOCTYPE declarations with external entity references
• Monitor application logs for XML parsing errors related to file access denials or network connection attempts
• Deploy network monitoring to identify suspicious outbound connections originating from the TEIGarage service
• Utilize endpoint detection tools to identify file access patterns indicative of XXE exploitation

Monitoring Recommendations

• Configure logging to capture all XML document submissions to conversion endpoints with full payload inspection
• Set up alerts for XML parsing exceptions that reference file system paths or internal network resources
• Monitor process file descriptors for unexpected access to sensitive system files
• Implement rate limiting and anomaly detection on conversion endpoints to identify reconnaissance activity

How to Mitigate CVE-2025-31497

Immediate Actions Required

• Upgrade TEIGarage to version 1.2.4 or later immediately to remediate this vulnerability
• If immediate upgrade is not possible, implement the workaround by configuring XMLConstants.FEATURE_SECURE_PROCESSING on all XML parsers
• Restrict network access to TEIGarage conversion endpoints using firewall rules or authentication mechanisms
• Review server logs for any indicators of prior exploitation attempts

Patch Information

The vulnerability has been patched in TEIGarage version 1.2.4. Organizations should update to this version as the primary remediation measure. For detailed patch information and upgrade instructions, refer to the GitHub Security Advisory.

Workarounds

• Configure the XML parser to disable external entity processing by enabling XMLConstants.FEATURE_SECURE_PROCESSING
• Disable DTD processing entirely if not required for document conversion functionality
• Implement input validation to strip or reject XML documents containing DOCTYPE declarations
• Deploy the service behind a reverse proxy that filters malicious XML patterns before reaching the application

The recommended parser configuration involves setting security features on the DocumentBuilderFactory or equivalent XML parser factory class. This includes disabling external general entities, external parameter entities, and DTD loading. The secure processing feature provides a comprehensive defense against XXE attacks by restricting the parser's ability to resolve external references.