# Deserialization of Untrusted Data (CWE-502)

The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.

**Stack:** JavaScript

- Prevalence: Mittel 3 Sprachen abgedeckt
- Impact: Kritisch 3 Regeln mit kritischem Schweregrad
- Prevention: Dokumentiert 7 Fix-Beispiele

**OWASP:** Software and Data Integrity Failures (A08:2021-Software and Data Integrity Failures) - #8

## Description

Many programming languages allow the serialization of objects for storage or transmission. When untrusted data is deserialized, it can lead to code execution, denial of service, or other unintended consequences.

## Prevention

Präventionsstrategien für Deserialization of Untrusted Data basierend auf 2 Shoulder-Erkennungsregeln.

### JavaScript

Validate training data against schemas and use content moderation before fine-tuning

Use JSON.parse() instead of node-serialize, and yaml.SAFE_SCHEMA for YAML parsing

## Warning Signs

- [HIGH] untrusted or unvalidated data flowing into AI/LLM fine-tuning or training
processes
- [CRITICAL] user input flowing to unsafe deserialization functions like node-serialize or yaml

## Consequences

- Nicht autorisierten Code ausführen
- DoS: Absturz/Beenden/Neustart
- Anwendungsdaten ändern

## Mitigations

- Wenn möglich, keine nicht vertrauenswürdigen Daten deserialisieren
- Falls Deserialisierung nötig ist, sicherere Formate wie JSON verwenden
- Integritätsprüfungen wie digitale Signaturen umsetzen
- Deserialisierung in Umgebungen mit geringen Rechten isolieren

## Detection

- Total rules: 7
- Critical: 3
- Languages: go, javascript, typescript, python

## Rules by Language

### Javascript (2 rules)

- **LLM Training Data Poisoning** [HIGH]: Detects untrusted or unvalidated data flowing into AI/LLM fine-tuning or training
processes. OWASP LLM03 - Training Data Poisoning.

Training data poisoning can:
- Introduce backdoors into model behavior
- Bias model outputs maliciously
- Embed harmful content that appears in responses
- Compromise model accuracy and reliability
- Create security vulnerabilities in model behavior

This rule detects:
- User-provided data used directly in fine-tuning
- External data sources used without validation
  - Remediation: Validate training data against schemas and use content moderation before fine-tuning.

```javascript
if (!validate(trainingData)) {
  return res.status(400).json({ error: 'Invalid format' });
}
await openai.files.create({ file: trainingData, purpose: 'fine-tune' });
```

Learn more: https://shoulder.dev/learn/javascript/cwe-502/llm-training-data-poisoning
- **Unsafe Deserialization** [CRITICAL]: Detects user input flowing to unsafe deserialization functions like node-serialize or yaml.load().
  - Remediation: Use JSON.parse() instead of node-serialize, or use yaml.SAFE_SCHEMA for YAML parsing.

```javascript
const data = JSON.parse(userInput);
// Or for YAML:
const config = yaml.load(input, { schema: yaml.SAFE_SCHEMA });
```

Learn more: https://shoulder.dev/learn/javascript/cwe-502/unsafe-deserialization

### Typescript (2 rules)

- **LLM Training Data Poisoning** [HIGH]: Detects untrusted or unvalidated data flowing into AI/LLM fine-tuning or training
processes. OWASP LLM03 - Training Data Poisoning.

Training data poisoning can:
- Introduce backdoors into model behavior
- Bias model outputs maliciously
- Embed harmful content that appears in responses
- Compromise model accuracy and reliability
- Create security vulnerabilities in model behavior

This rule detects:
- User-provided data used directly in fine-tuning
- External data sources used without validation
  - Remediation: Validate training data against schemas and use content moderation before fine-tuning.

```javascript
if (!validate(trainingData)) {
  return res.status(400).json({ error: 'Invalid format' });
}
await openai.files.create({ file: trainingData, purpose: 'fine-tune' });
```

Learn more: https://shoulder.dev/learn/javascript/cwe-502/llm-training-data-poisoning
- **Unsafe Deserialization** [CRITICAL]: Detects user input flowing to unsafe deserialization functions like node-serialize or yaml.load().
  - Remediation: Use JSON.parse() instead of node-serialize, or use yaml.SAFE_SCHEMA for YAML parsing.

```javascript
const data = JSON.parse(userInput);
// Or for YAML:
const config = yaml.load(input, { schema: yaml.SAFE_SCHEMA });
```

Learn more: https://shoulder.dev/learn/javascript/cwe-502/unsafe-deserialization