# Time-of-Check Time-of-Use (TOCTOU) Race Condition

- ID: python-toctou-race-condition
- Severity: MEDIUM
- CWE: CWE-367 (CWE-367)
- Languages: Python

## Description

Detects potential race conditions where a resource is checked (exists, permissions)
and then used later. Between check and use, the resource state can change,
leading to security issues. Use atomic operations or proper locking instead.

## Remediation

Use atomic operations instead of check-then-use patterns.

```python
def read_file_safely(filename):
    try:
        with open(filename, 'r') as f:
            return f.read()
    except FileNotFoundError:
        return None

def create_file_safely(filename, content):
    with open(filename, 'x') as f:  # 'x' mode is atomic
        f.write(content)
```

Learn more: https://shoulder.dev/learn/python/cwe-367/race-condition

## Documentation

[object Object]