# Improper Handling of Unicode Encoding (CWE-176)

The product does not properly handle when an input contains Unicode encoding.

**Stack:** Python

- Prevalence: Média 3 linguagens cobertas
- Impact: Médio Revisão recomendada
- Prevention: Documentada 3 exemplos de correção

**OWASP:** Injection (A03:2021-Injection) - #3

## Description

Unicode characters can have multiple encodings or representations. If an application does not properly handle Unicode, attackers may be able to bypass security filters or cause unexpected behavior using alternate encodings.

## Prevention

Estratégias de prevenção para Improper Handling of Unicode baseadas em 1 regras de detecção do Shoulder.

### Python

Normalize Unicode strings with NFKC before comparison or security-critical operations

## Warning Signs

- [MEDIUM] missing Unicode normalization leading to security bypasses

## Consequences

- Burlar mecanismo de proteção
- Executar código não autorizado

## Mitigations

- Normalize entradas Unicode para uma forma canônica antes de processar
- Aplique verificações de segurança após a normalização Unicode
- Use funções de comparação que entendam Unicode

## Detection

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

## Rules by Language

### Python (1 rules)

- **Unicode Normalization Issues** [MEDIUM]: Detects missing Unicode normalization leading to security bypasses.
  - Remediation: Normalize Unicode strings before comparison using unicodedata.normalize().

```python
import unicodedata

def normalize_username(username):
    return unicodedata.normalize('NFKC', username).lower()

if normalize_username(input_name) == normalize_username(stored_name):
    grant_access()
```

Learn more: https://shoulder.dev/learn/python/cwe-176/unicode-normalization