# Deserialization of Untrusted Data (CWE-502)

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

**Stack:** Go

- Prevalence: 中 3 言語をカバー
- Impact: クリティカル 3 件の重大度クリティカルなルール
- Prevention: 文書化済み 7 件の修正例

**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

2 件の Shoulder 検出ルールに基づく Deserialization of Untrusted Data の予防策。

### Go

Use strict typed structs instead of interface{} and avoid gob with untrusted data

Validate all training data against strict schemas and apply content moderation before ingestion

## Warning Signs

- [HIGH] Untrusted data is deserialized without validation
- [HIGH] truly dangerous deserialization in Go
- [HIGH] Untrusted data flows to ... without validation
- [HIGH] untrusted data flowing into AI/LLM fine-tuning or training processes without validation

## Consequences

- 未承認コードの実行
- DoS: クラッシュ/終了/再起動
- アプリケーションデータの変更

## Mitigations

- 可能であれば、信頼できないデータのデシリアライズを避ける
- デシリアライズが必要な場合は、JSON のようなより安全な形式を使用する
- デジタル署名などの完全性チェックを実装する
- デシリアライズは低権限環境に隔離する

## Detection

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

## Rules by Language

### Go (2 rules)

- **Insecure Deserialization** [HIGH]: Detects truly dangerous deserialization in Go. Unlike Java or Python, Go's encoding/json
is safe (data-only parsing, no code execution). This rule focuses on:
- gob.Decoder: Can instantiate arbitrary types, potential RCE (CRITICAL)
- json/yaml/xml to interface{}: Type confusion risk when combined with untrusted input (MEDIUM)

Note: json.Unmarshal to typed structs is NOT flagged as it cannot execute code.
  - Remediation: Use strict struct types instead of interface{} and validate after unmarshaling.

```go
type User struct {
    Name  string `json:"name"`
    Email string `json:"email"`
}

var user User
if err := json.Unmarshal(input, &user); err != nil {
    return err
}
```

Learn more: https://shoulder.dev/learn/go/cwe-502/unsafe-deserialization
- **LLM Training Data Poisoning** [HIGH]: Detects untrusted data flowing into AI/LLM fine-tuning or training processes without validation.
  - Remediation: Validate all training data against strict schemas before ingestion.

```go
if err := validate.Struct(doc); err != nil {
    return errors.New("validation failed")
}
```

Learn more: https://shoulder.dev/learn/go/cwe-502/llm-training-data-poisoning