# Insecure Temporary File (CWE-377)

Creating and using insecure temporary files can leave application and system data vulnerable to attack.

- Prevalence: Medium 1 language covered
- Impact: Medium Review recommended
- Prevention: Documented 1 fix examples

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

## Description

Temporary files that are created with predictable names, insecure permissions, or in shared directories can be exploited by attackers to read or modify sensitive data, or to inject malicious content.

## Prevention

### Key Practices

- Use tempfile

### Python

Use tempfile.NamedTemporaryFile or tempfile.mkstemp instead of mktemp

## Warning Signs

- [MEDIUM] insecure temporary file creation using tempfile

## Consequences

- Read Application Data
- Modify Application Data
- Execute Unauthorized Code

## Mitigations

- Use secure temporary file creation functions (e.g., mkstemp)
- Create temporary files in secure, non-world-writable directories
- Set restrictive permissions on temporary files

## Detection

- Total rules: 1
- Languages: python

## Rules by Language

### Python (1 rules)

- **Insecure Temporary File Creation** [MEDIUM]: Detects insecure temporary file creation using tempfile.mktemp(), predictable
names, or world-readable permissions. These can lead to symlink attacks, race
conditions, or information disclosure. Use tempfile.mkstemp() or NamedTemporaryFile.
  - Remediation: Use tempfile.NamedTemporaryFile or tempfile.mkstemp instead of mktemp().

```python
import tempfile

with tempfile.NamedTemporaryFile(mode='w+', delete=True) as tmp:
    tmp.write(data)
    tmp.flush()
    result = process_file(tmp.name)
```

Learn more: https://shoulder.dev/learn/python/cwe-377/insecure-tempfile