# Unchecked Return Value (CWE-252)

The product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions.

- Prevalence: Media 2 lenguajes cubiertos
- Impact: Alto 1 reglas de severidad alta
- Prevention: Documentada 2 ejemplos de corrección

**OWASP:** Insecure Design (A04:2021-Insecure Design) - #4

## Description

When return values are not checked, the program may continue execution in an error state or with incorrect data, potentially leading to security vulnerabilities.

## Prevention

Estrategias de prevención para Unchecked Return Value basadas en 2 reglas de detección de Shoulder.

### Go

Replace blank identifier _ with err and check error return values

### JavaScript

Always check return values from critical operations like password comparison and database writes

## Warning Signs

- [HIGH] Return value from ... at ... is not checked
- [HIGH] critical operations (file system, database, authentication) whose
return values are not checked

## Consequences

- DoS
- Ejecutar código no autorizado
- Modificar datos de la aplicación

## Mitigations

- Verifica siempre los valores de retorno de las funciones
- Usa las advertencias del compilador para detectar valores de retorno no verificados
- Maneja las condiciones de error adecuadamente

## Detection

- Total rules: 2
- Languages: go, javascript, typescript

## Rules by Language

### Go (1 rules)

- **Unchecked Error Return Values** [MEDIUM]: Error return value ignored using blank identifier (_).
  - Remediation: Check all error return values and handle appropriately.

```go
data, err := ioutil.ReadFile(path)
if err != nil {
    return fmt.Errorf("failed to read file: %w", err)
}
```

Learn more: https://shoulder.dev/learn/go/cwe-252/unchecked-errors

### Javascript (1 rules)

- **Unchecked Return Value from Critical Operations** [HIGH]: Detects critical operations (file system, database, authentication) whose
return values are not checked. Ignoring return values can lead to silent
failures, data corruption, and security vulnerabilities.

Critical operations that must have their return values checked include:
- File system operations (write, delete, chmod)
- Database operations (insert, update, delete)
- Authentication/authorization checks
- Cryptographic operations
  - Remediation: Always check return values from critical operations:

```javascript
// ✅ SAFE - Check return value
const result = await fs.writeFile(path, data);
if (!result.success) {
  logger.error('Write failed');
  throw new Error('Failed to write file');
}
```

### Typescript (1 rules)

- **Unchecked Return Value from Critical Operations** [HIGH]: Detects critical operations (file system, database, authentication) whose
return values are not checked. Ignoring return values can lead to silent
failures, data corruption, and security vulnerabilities.

Critical operations that must have their return values checked include:
- File system operations (write, delete, chmod)
- Database operations (insert, update, delete)
- Authentication/authorization checks
- Cryptographic operations
  - Remediation: Always check return values from critical operations:

```javascript
// ✅ SAFE - Check return value
const result = await fs.writeFile(path, data);
if (!result.success) {
  logger.error('Write failed');
  throw new Error('Failed to write file');
}
```