# NULL Pointer Dereference (CWE-476)

A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL.

**Stack:** Go

- Prevalence: 보통 2개 언어 지원
- Impact: 보통 검토 권장
- Prevention: 문서화됨 2개의 수정 예시

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

## Description

NULL pointer dereferences typically cause the application to crash. In some cases, they may be exploitable for denial of service or potentially for code execution.

## Prevention

### Go

Use the two-value form of type assertion or type switch to handle failures gracefully

## Consequences

- DoS: 충돌/종료/재시작

## Mitigations

- 포인터를 역참조하기 전에 확인하세요
- 널 포인터 문제를 방지하는 언어 기능을 활용하세요
- null 반환에 대한 적절한 오류 처리를 구현하세요

## Detection

- Total rules: 2
- Languages: go, typescript

## Rules by Language

### Go (1 rules)

- **Unsafe Type Assertion Without Ok Check** [MEDIUM]: Type assertion without two-value form can panic at runtime.
  - Remediation: Use the two-value form of type assertion to handle failures gracefully.

```go
result, ok := data.(map[string]interface{})
if !ok {
    return errors.New("invalid data type")
}
```

Learn more: https://shoulder.dev/learn/go/cwe-476/unsafe-type-assertion