# Improper Restriction of XML External Entity Reference (CWE-611)

The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.

**Stack:** Python

- Prevalence: Moyenne 3 langages couverts
- Impact: Élevé 3 règles de sévérité élevée
- Prevention: Documentée 3 exemples de correctifs

**OWASP:** Security Misconfiguration (A05:2021-Security Misconfiguration) - #5

## Description

XML External Entity (XXE) attacks exploit features of XML parsers to read local files, perform server-side request forgery, or cause denial of service.

## Prevention

Stratégies de prévention pour XML External Entity (XXE) basées sur 1 règles de détection Shoulder.

### Key Practices

- Use denial of service

### Python

Use defusedxml instead of standard XML parsers for untrusted input

## Warning Signs

- [HIGH] XML parsing with external entity processing enabled

## Consequences

- Lecture des données de l'application
- Lire des fichiers ou des répertoires
- DoS

## Mitigations

- Désactivez le traitement des entités externes dans les analyseurs XML
- Utilisez des formats de données moins complexes comme JSON lorsque c'est possible
- Validez et assainissez les entrées XML

## Detection

- Total rules: 3
- Languages: go, javascript, typescript, python

## Rules by Language

### Python (1 rules)

- **XML External Entity (XXE) Injection** [HIGH]: Detects XML parsing with external entity processing enabled. XXE attacks
allow attackers to read local files, perform SSRF, or cause denial of service.
Always disable external entity processing when parsing untrusted XML.
  - Remediation: Use defusedxml instead of standard XML parsers for untrusted input.

```python
import defusedxml.ElementTree as ET
from flask import request, jsonify

@app.route('/api/xml', methods=['POST'])
def parse_xml():
    try:
        root = ET.fromstring(request.data)
        return jsonify({'name': root.find('name').text})
    except ET.ParseError:
        return jsonify({'error': 'Invalid XML'}), 400
```

Learn more: https://shoulder.dev/learn/python/cwe-611/xxe