CVE-2021-25951
📋 TL;DR
CVE-2021-25951 is an XML External Entity (XXE) vulnerability in XML2Dict version 0.2.2 that allows attackers to cause denial of service by parsing malicious XML files. This affects applications using the vulnerable XML2Dict library to process untrusted XML input. Developers and systems using XML2Dict 0.2.2 for XML parsing are at risk.
💻 Affected Systems
- XML2Dict
📦 What is this software?
Xml2dict by Xml2dict Project
⚠️ Risk & Real-World Impact
Worst Case
Complete system unavailability through resource exhaustion or crash when processing malicious XML payloads
Likely Case
Application denial of service causing service disruption and potential data loss
If Mitigated
Minimal impact with proper input validation and XML parser configuration
🎯 Exploit Status
XXE vulnerabilities are well-understood with readily available exploit techniques
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.2.3 and later
Vendor Advisory: https://github.com/amirziai/xml2dict
Restart Required: No
Instructions:
1. Update XML2Dict: pip install --upgrade xml2dict
2. Verify version: pip show xml2dict
3. Restart any services using the library
🔧 Temporary Workarounds
Disable external entity processing
allConfigure XML parser to disable external entity resolution
Modify code to use defusedxml library or set resolve_entities=False in parser configuration
Input validation and sanitization
allValidate and sanitize XML input before processing
Implement XML schema validation or strip dangerous XML constructs
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable systems
- Deploy web application firewall with XXE protection rules
🔍 How to Verify
Check if Vulnerable:
Check installed version: pip show xml2dict | grep VersionCheck Version:
pip show xml2dict | grep VersionVerify Fix Applied:
Confirm version is 0.2.3 or higher: pip show xml2dict | grep Version📡 Detection & Monitoring
Log Indicators:
- Unusual XML parsing errors
- Memory exhaustion alerts
- Process crashes during XML processing
Network Indicators:
- Large XML payloads with external entity references
- Unusual outbound connections from XML parsers
SIEM Query:
source="application.logs" AND ("XML parsing error" OR "memory exhaustion" OR "xml2dict")