# 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: 中 覆盖 2 种语言
- Impact: 高 1 条严重级别为高的规则
- Prevention: 已记录 2 个修复示例

**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

基于 2 条 Shoulder 检测规则的 Unchecked Return Value 预防策略。

### 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

- 拒绝服务 (DoS)
- 执行未授权代码
- 修改应用程序数据

## Mitigations

- 始终检查函数的返回值
- 使用编译器警告检测未检查的返回值
- 适当地处理错误情况

## 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');
}
```