# Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) (CWE-338)

The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.

**Stack:** JavaScript

- Prevalence: 高 頻繁に悪用される
- Impact: ハイ 2 件の重大度ハイのルール
- Prevention: 文書化済み 4 件の修正例

**OWASP:** Cryptographic Failures (A02:2021-Cryptographic Failures) - #2

## Description

When a non-cryptographic PRNG is used in a security context (such as generating session tokens or cryptographic keys), an attacker may be able to predict its output and compromise the security mechanism.

## Prevention

1 件の Shoulder 検出ルールに基づく Weak PRNG の予防策。

### Key Practices

- Use of Math

### JavaScript

Use crypto.randomBytes() or crypto.randomUUID() for security-sensitive random values

## Warning Signs

- [HIGH] Math.random() used for security-sensitive operation: ...
- [HIGH] use of Math

## Consequences

- 保護メカニズムの回避
- 権限の取得

## Mitigations

- 暗号学的に安全な乱数生成器 (CSPRNG) を使用する
- JavaScript では crypto.getRandomValues() または crypto.randomUUID() を使用する
- Python では random ではなく secrets モジュールを使用する

## Detection

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

## Rules by Language

### Javascript (1 rules)

- **Weak Random Number Generation in Security Context** [HIGH]: Detects use of Math.random() for security-sensitive operations like generating
tokens, session IDs, or cryptographic keys. Math.random() is not cryptographically
secure and can be predicted by attackers.
  - Remediation: Replace Math.random() with cryptographically secure alternatives.

### Typescript (1 rules)

- **Weak Random Number Generation in Security Context** [HIGH]: Detects use of Math.random() for security-sensitive operations like generating
tokens, session IDs, or cryptographic keys. Math.random() is not cryptographically
secure and can be predicted by attackers.
  - Remediation: Replace Math.random() with cryptographically secure alternatives.