no-ecb-mode

📡 Live from GitHub — This documentation is fetched directly from no-ecb-mode.md and cached for 6 hours.

Keywords: ECB, encryption mode, block cipher, ECB penguin, CWE-327, security, ESLint rule, LLM-optimized CWE: CWE-327
OWASP: A02:2021-Cryptographic Failures

Disallow ECB encryption mode (use GCM or CBC instead)

Detects usage of ECB (Electronic Codebook) encryption mode which leaks data patterns. This rule is part of eslint-plugin-node-security and provides LLM-optimized error messages with fix suggestions.

🚨 Security rule | 💡 Provides suggestions | ⚠️ Set to error in recommended

Quick Summary

Aspect	Details
CWE Reference	CWE-327 (Broken Crypto)
Severity	High (security vulnerability)
Auto-Fix	💡 Suggests fixes (GCM, CBC)
Category	Security
ESLint MCP	✅ Optimized for ESLint MCP integration
Best For	Node.js applications using symmetric encryption

Vulnerability and Risk

Vulnerability: ECB mode encrypts identical plaintext blocks to identical ciphertext blocks. This means patterns in the plaintext are preserved in the ciphertext, leaking information about the data structure.

Risk: The famous "ECB Penguin" demonstrates this perfectly - an encrypted image still shows the original image's structure. This weakness can reveal message lengths, patterns, and repeated data to attackers.

Rule Details

This rule detects ECB mode usage in crypto.createCipheriv() calls (e.g., aes-128-ecb, aes-256-ecb) and suggests using GCM or CBC mode instead.

Why This Matters

Risk	Impact	Solution
🎨 Pattern Leakage	Data patterns visible in ciphertext	Use GCM or CBC mode
📊 Block Analysis	Repeated blocks reveal repeated data	Use authenticated encryption
🔒 Compliance	Fails security audits and pen tests	Replace all ECB usage

Configuration

Option	Type	Default	Description
`allowInTests`	`boolean`	`false`	Allow ECB mode in test files

{
  rules: {
    'node-security/no-ecb-mode': ['error', {
      allowInTests: false
    }]
  }
}

Examples

❌ Incorrect

import crypto from 'crypto';

// ECB mode leaks patterns - HIGH risk
const cipher = crypto.createCipheriv('aes-128-ecb', key, null);

// AES-256-ECB - still insecure despite key size
const strongKeyEcb = crypto.createCipheriv('aes-256-ecb', key, null);

✅ Correct

import crypto from 'crypto';

// GCM mode - authenticated encryption (recommended)
const iv = crypto.randomBytes(16);
const cipher = crypto.createCipheriv('aes-256-gcm', key, iv);

// CBC mode with random IV
const cbcCipher = crypto.createCipheriv('aes-256-cbc', key, iv);

// ChaCha20-Poly1305 - authenticated stream cipher
const chachaCipher = crypto.createCipheriv('chacha20-poly1305', key, iv);

The ECB Penguin

ECB Penguin

The "ECB Penguin" is a famous example showing how ECB mode preserves patterns. The original Tux penguin image, when encrypted with ECB mode, still shows the penguin's outline because identical pixel blocks produce identical ciphertext blocks.

Security Impact

Vulnerability	CWE	OWASP	CVSS	Impact
Broken Crypto	327	A02:2021	5.9 Medium	Pattern leakage
Information Exposure	200	A02:2021	5.3 Medium	Data structure revealed

Migration Guide

Phase 1: Discovery

{
  rules: {
    'node-security/no-ecb-mode': 'warn'
  }
}

Phase 2: Replacement

// Replace ECB with GCM
crypto.createCipheriv('aes-256-ecb', key, null); // ❌ Before
crypto.createCipheriv('aes-256-gcm', key, iv); // ✅ After

Phase 3: Enforcement

{
  rules: {
    'node-security/no-ecb-mode': 'error'
  }
}

no-weak-cipher-algorithm - Detect weak encryption algorithms
no-static-iv - Detect hardcoded initialization vectors
no-deprecated-cipher-method - Detect deprecated cipher methods

Known False Negatives

Dynamic Mode Strings

Why: Dynamic strings cannot be analyzed statically.

// ❌ NOT DETECTED
const mode = config.cipherMode;
crypto.createCipheriv(`aes-256-${mode}`, key, iv);

Mitigation: Use constants for cipher specifications.