# Non-Null Assertion Without Null Check

- ID: typescript-non-null-assertion
- Severity: LOW
- CWE: CWE-476 (CWE-476)
- Languages: TypeScript
- Frameworks: express, fastify, nestjs, next

## Description

The non-null assertion operator (!) bypasses null/undefined checks at compile time
without runtime safety, causing crashes when values are unexpectedly null.

## Detection Message

Non-null assertion (!), used on '{expression}' without explicit null/undefined check. This may cause runtime crashes if the value is null/undefined.

## Remediation

Use explicit null checks or optional chaining instead of non-null assertions.

```typescript
function getUserEmail(userId: string) {
  const user = users.find(u => u.id === userId);
  if (!user) {
    throw new Error('User not found');
  }
  return user.email;
}
```

Learn more: https://shoulder.dev/learn/typescript/cwe-476/non-null-assertion

## Documentation

[object Object]

## Related Rules

- **Unsafe Type Assertion Without Ok Check** [MEDIUM]: