# Improper Output Neutralization for Logs (CWE-117)

The product does not neutralize or incorrectly neutralizes output that is written to logs.

**Stack:** JavaScript

- Prevalence: Mittel 3 Sprachen abgedeckt
- Impact: Mittel Review empfohlen
- Prevention: Dokumentiert 4 Fix-Beispiele

**OWASP:** Injection (A03:2021-Injection) - #3

## Description

Log injection attacks occur when user input is written to log files without proper sanitization. This can allow attackers to forge log entries, inject malicious content, or exploit log analysis tools.

## Prevention

Präventionsstrategien für Log Injection basierend auf 2 Shoulder-Erkennungsregeln.

### JavaScript

Strip newline characters from user input before writing to log files

Sanitize user input by stripping CRLF characters before writing to logs

## Warning Signs

- [LOW] user input flowing to persistent log files without sanitization

## Consequences

- Anwendungsdaten ändern
- Aktivitäten verbergen
- Nicht autorisierten Code ausführen

## Mitigations

- Validiere und bereinige alle Eingaben, bevor sie in Logs geschrieben werden
- Verwende strukturierte Log-Formate, die Daten von der Log-Syntax trennen
- Encodiere Sonderzeichen, wenn benutzergesteuerte Daten in Logs geschrieben werden

## Detection

- Total rules: 4
- Languages: go, javascript, typescript, python

## Rules by Language

### Javascript (2 rules)

- **Log Injection** [LOW]: Detects user input flowing to persistent log files without sanitization.
  - Remediation: Sanitize user input by removing newline characters before logging.

```javascript
const safe = userInput.replace(/[\r\n]/g, '');
logger.info(safe);
```

Learn more: https://shoulder.dev/learn/javascript/cwe-117/log-injection
- **Log Injection** [MEDIUM]: Detects user input flowing to persistent log files without sanitization.
  - Remediation: Sanitize user input before logging to prevent log forgery:

```javascript
const sanitize = (str) => str.replace(/[\r\n]/g, '').substring(0, 200);
logger.info('Login attempt', { username: sanitize(req.body.username) });
```

Learn more: https://shoulder.dev/learn/javascript/cwe-117/log-injection

### Typescript (1 rules)

- **Log Injection** [MEDIUM]: Detects user input flowing to persistent log files without sanitization.
  - Remediation: Sanitize user input before logging to prevent log forgery:

```javascript
const sanitize = (str) => str.replace(/[\r\n]/g, '').substring(0, 200);
logger.info('Login attempt', { username: sanitize(req.body.username) });
```

Learn more: https://shoulder.dev/learn/javascript/cwe-117/log-injection