# Cwe 329 Missing Random Iv

> Use this skill when you need to remediate CWE-329 (Missing Random IV in CBC Mode) vulnerabilities in Java code. Triggers on SAST findings, security reviews, or when fixing missing random iv in cbc mode issues.

- Skill: `developerscoffee/cwe-329-missing-random-iv` (Agent Skill)
- Install (CLI): `npx skillmds@latest add developerscoffee/cwe-329-missing-random-iv`
- Raw SKILL.md: https://api.skillmd.com/api/skills/developerscoffee/cwe-329-missing-random-iv/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Security
- License: MIT
- Author: DevelopersCoffee (https://skillmd.com/u/developerscoffee)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/developerscoffee/cwe-329-missing-random-iv

---


# CWE-329 Missing Random IV in CBC Mode

## Description

Missing Random IV in CBC Mode

Reference:
https://cwe.mitre.org/data/definitions/329.html


**OWASP Category**: A02:2021 – Cryptographic Failures


---

## Vulnerable Pattern


### ❌ Example 1: Vulnerable Pattern

```java
// VULNERABLE: Static IV reused
private static final byte[] STATIC_IV = "1234567890123456".getBytes();

Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, key, new IvParameterSpec(STATIC_IV));
```


**Why it's vulnerable:** This pattern is vulnerable to Missing Random IV in CBC Mode




---

## Deterministic Fix


### ✅ Secure Implementation: Secure Implementation

```java
// SECURE: Generate random IV for each encryption
public byte[] encrypt(byte[] plaintext, SecretKey key) throws Exception {
    // Generate random IV
    byte[] iv = new byte[16];
    new SecureRandom().nextBytes(iv);

    Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");  // GCM preferred
    cipher.init(Cipher.ENCRYPT_MODE, key, new GCMParameterSpec(128, iv));
    byte[] ciphertext = cipher.doFinal(plaintext);

    // Prepend IV to ciphertext for decryption
    byte[] result = new byte[iv.length + ciphertext.length];
    System.arraycopy(iv, 0, result, 0, iv.length);
    System.arraycopy(ciphertext, 0, result, iv.length, ciphertext.length);
    return result;
}
```


**Why it's secure:** Implements proper protection against Missing Random IV in CBC Mode




---

## Detection Pattern

Look for these patterns in your codebase:


```bash
# Find static IV patterns
grep -rn "IvParameterSpec.*static\|final.*IV" --include="*.java"
```



---

## Remediation Steps


1. Generate new random IV for each encryption operation

2. Use SecureRandom for IV generation

3. Prefer AES-GCM over AES-CBC for authenticated encryption

4. Store IV with ciphertext (it's not secret)


---

## Key Imports

```java

import java.security.SecureRandom;

import javax.crypto.spec.GCMParameterSpec;

```

---

## Verification

After remediation:


- Run SAST scanner to confirm vulnerability is resolved

- Review all instances of the vulnerable pattern

- Add unit tests that verify the secure implementation

- Check for similar patterns in related code


---

## Trigger Examples

```
Fix CWE-329 vulnerability
Resolve Missing Random IV in CBC Mode issue
Secure this Java code against missing random iv in cbc mode
SAST reports CWE-329
```

---

## Common Vulnerable Locations

| Layer | Files | Patterns |
|-------|-------|----------|

| Controller | `*Controller.java` | User input handling |

| Service | `*Service.java` | Business logic |

| Repository | `*Repository.java` | Data access |


---

## References


- [CWE-329: Not Using Random IV](https://cwe.mitre.org/data/definitions/329.html)


---

**Source**: Generated by [Java CWE Security Skills Generator](https://github.com/DevelopersCoffee/java-cwe-security-skills)
**Last Updated**: 2026-03-07