# 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:** Go

- Prevalence: Media 3 lenguajes cubiertos
- Impact: Alto 3 reglas de severidad alta
- Prevention: Documentada 3 ejemplos de corrección

**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

Estrategias de prevención para XML External Entity (XXE) basadas en 1 reglas de detección de Shoulder.

### Go

Go's encoding/xml is safe by default; reject XML with DOCTYPE declarations as defense in depth

## Consequences

- Leer datos de la aplicación
- Leer archivos o directorios
- DoS

## Mitigations

- Desactiva el procesamiento de entidades externas en los parsers XML
- Usa formatos de datos menos complejos como JSON cuando sea posible
- Valida y sanea las entradas XML

## Detection

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

## Rules by Language

### Go (1 rules)

- **XML External Entity (XXE) Injection** [HIGH]: User-controlled XML parsed without disabling external entities.
  - Remediation: Go's encoding/xml is safe by default. Reject XML with DOCTYPE declarations.

```go
if bytes.Contains(body, []byte("<!DOCTYPE")) {
    return errors.New("DOCTYPE not allowed")
}
var data MyStruct
xml.Unmarshal(body, &data)
```

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