# Improper Handling of Exceptional Conditions (CWE-755)

The product does not handle or incorrectly handles an exceptional condition.

**Stack:** JavaScript

- Prevalence: 中 3 言語をカバー
- Impact: ハイ 1 件の重大度ハイのルール
- Prevention: 文書化済み 4 件の修正例

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

## Description

When exceptional conditions are not properly handled, the product may enter an undefined state, crash, or expose sensitive information. This can lead to denial of service, information disclosure, or unexpected behavior.

## Prevention

1 件の Shoulder 検出ルールに基づく Improper Handling of Exceptional Conditions の予防策。

### JavaScript

Use finally blocks to release resources (connections, file handles) on all code paths

## Warning Signs

- [MEDIUM] Resource at ... may not be released when exceptions occur
- [MEDIUM] code that allocates resources (files, connections, memory) within
try blocks but fails to release th

## Consequences

- DoS
- アプリケーションデータの読み取り
- 未承認コードの実行

## Mitigations

- 起こり得るすべての例外的状況を想定し、適切に処理する
- try-catch ブロックと適切なエラー処理メカニズムを使用する
- 例外発生時はセキュアにフェイルする

## Detection

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

## Rules by Language

### Javascript (1 rules)

- **Resource Exhaustion via Exception Handling** [MEDIUM]: Detects code that allocates resources (files, connections, memory) within
try blocks but fails to release them in finally blocks or error paths.

When exceptions occur, resources may not be properly cleaned up, leading
to resource exhaustion, memory leaks, and denial of service.
  - Remediation: Use finally blocks or try-with-resources pattern:

```javascript
// ✅ SAFE - Cleanup in finally
let connection;
try {
  connection = await db.getConnection();
  await connection.query(sql);
} catch (error) {
  logger.error('Query failed:', error);
  throw error;
} finally {
  if (connection) {
    await connection.release();
  }
}
```

### Typescript (1 rules)

- **Resource Exhaustion via Exception Handling** [MEDIUM]: Detects code that allocates resources (files, connections, memory) within
try blocks but fails to release them in finally blocks or error paths.

When exceptions occur, resources may not be properly cleaned up, leading
to resource exhaustion, memory leaks, and denial of service.
  - Remediation: Use finally blocks or try-with-resources pattern:

```javascript
// ✅ SAFE - Cleanup in finally
let connection;
try {
  connection = await db.getConnection();
  await connection.query(sql);
} catch (error) {
  logger.error('Query failed:', error);
  throw error;
} finally {
  if (connection) {
    await connection.release();
  }
}
```