What is Use of Insufficiently Random Values (CWE-330)?

TL;DR: Use of Insufficiently Random Values (CWE-330) is a type of Cryptographic Failures vulnerability that occurs when a product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers. To prevent CWE-330 vulnerabilities, use well-vetted algorithms and select well-tested implementations with adequate length seeds.

At-a-Glance Table

What is Use of Insufficiently Random Values?

Use of Insufficiently Random Values (CWE-330) is a type of Cryptographic Failures vulnerability that occurs when a product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers. As defined by the MITRE Corporation under CWE-330, and classified by the OWASP Foundation under A04:2025 - Cryptographic Failures, this vulnerability can lead to potential exploitation and data breaches.

Quick Summary

Use of Insufficiently Random Values (CWE-330) is a critical security vulnerability that occurs when a product uses insufficiently random numbers or values in a security context. This vulnerability can lead to confidentiality breaches, integrity violations, and availability disruptions. To prevent CWE-330 vulnerabilities, use well-vetted algorithms and select well-tested implementations with adequate length seeds.

Jump to: Quick Summary · Use of Insufficiently Random Values Overview · How Use of Insufficiently Random Values Works · Business Impact of Use of Insufficiently Random Values · Use of Insufficiently Random Values Attack Scenario · How to Detect Use of Insufficiently Random Values · How to Fix Use of Insufficiently Random Values · Framework-Specific Fixes for Use of Insufficiently Random Values · How to Ask AI to Check Your Code for Use of Insufficiently Random Values · Use of Insufficiently Random Values Best Practices Checklist · Use of Insufficiently Random Values FAQ · Vulnerabilities Related to Use of Insufficiently Random Values · References · Scan Your Own Site

Use of Insufficiently Random Values Overview

What: Use of Insufficiently Random Values (CWE-330) is a type of Cryptographic Failures vulnerability that occurs when a product uses insufficiently random numbers or values in a security context.

Why it matters: CWE-330 vulnerabilities can lead to potential exploitation and data breaches, compromising confidentiality, integrity, and availability.

Where it occurs: CWE-330 vulnerabilities occur in products that use pseudo-random number generators (PRNGs) without adequate length seeds or well-vetted algorithms.

Who is affected: Any product that uses PRNGs without adequate length seeds or well-vetted algorithms can be vulnerable to CWE-330 attacks.

Who is NOT affected: Products that use well-vetted algorithms and select well-tested implementations with adequate length seeds are not vulnerable to CWE-330 attacks.

How Use of Insufficiently Random Values Works

Root Cause

The root cause of CWE-330 vulnerabilities is the use of insufficiently random numbers or values in a security context. This can occur when a product uses PRNGs without adequate length seeds or well-vetted algorithms.

Attack Flow

1. An attacker attempts to guess or brute-force the ID or key used for authentication or encryption.
2. The attacker successfully guesses or brute-forces the ID or key, gaining access to sensitive data or systems.
3. The attacker exploits the vulnerability to compromise confidentiality, integrity, and availability.

Prerequisites to Exploit

• The product must use PRNGs without adequate length seeds or well-vetted algorithms.
• The attacker must have access to the system or network where the vulnerable product is running.

Vulnerable Code

import random

def generate_id():
    return str(random.randint(1, 1000))

id = generate_id()
print(id)

This code generates a pseudo-random ID using the random module. However, this ID may not be sufficiently random to prevent attacks.

Secure Code

import secrets

def generate_id():
    return str(secrets.randbelow(1000))

id = generate_id()
print(id)

This code generates a cryptographically secure pseudo-random ID using the secrets module. This ID is more resistant to attacks and provides better security.

Business Impact of Use of Insufficiently Random Values

Confidentiality: CWE-330 vulnerabilities can lead to confidentiality breaches, where sensitive data or systems are compromised.

• Financial impact: Loss of sensitive data or systems can result in significant financial losses.
• Compliance impact: CWE-330 vulnerabilities can lead to non-compliance with regulatory requirements, resulting in fines and reputational damage.
• Reputation impact: CWE-330 vulnerabilities can compromise the reputation of an organization, leading to loss of customer trust.

Integrity: CWE-330 vulnerabilities can lead to integrity violations, where data or systems are modified without authorization.

• Financial impact: Loss of sensitive data or systems can result in significant financial losses.
• Compliance impact: CWE-330 vulnerabilities can lead to non-compliance with regulatory requirements, resulting in fines and reputational damage.
• Reputation impact: CWE-330 vulnerabilities can compromise the reputation of an organization, leading to loss of customer trust.

Availability: CWE-330 vulnerabilities can lead to availability disruptions, where data or systems are unavailable due to attacks.

• Financial impact: Loss of revenue due to system downtime or data unavailability.
• Compliance impact: CWE-330 vulnerabilities can lead to non-compliance with regulatory requirements, resulting in fines and reputational damage.
• Reputation impact: CWE-330 vulnerabilities can compromise the reputation of an organization, leading to loss of customer trust.

Use of Insufficiently Random Values Attack Scenario

1. An attacker attempts to guess or brute-force the ID or key used for authentication or encryption.
2. The attacker successfully guesses or brute-forces the ID or key, gaining access to sensitive data or systems.
3. The attacker exploits the vulnerability to compromise confidentiality, integrity, and availability.

How to Detect Use of Insufficiently Random Values

Manual Testing

• Review code for insufficiently random numbers or values in a security context.
• Test products with well-vetted algorithms and select well-tested implementations with adequate length seeds.

Automated Scanners (SAST / DAST)

• Use automated scanners to identify potential CWE-330 vulnerabilities.
• Contrast what static analysis catches here vs. what needs dynamic/runtime testing to find, specific to this weakness.

PenScan Detection

• PenScan’s scanner engines actively test for CWE-330 vulnerabilities, ensuring you catch potential issues before an attacker does.

False Positive Guidance

• Be cautious of false positives when detecting CWE-330 vulnerabilities.
• Use manual testing and automated scanners in conjunction with PenScan detection to ensure accurate results.

How to Fix Use of Insufficiently Random Values

• Use well-vetted algorithms that are currently considered strong by experts in the field.
• Select well-tested implementations with adequate length seeds.
• Consider a PRNG that re-seeds itself as needed from high-quality pseudo-random output sources.

Framework-Specific Fixes for Use of Insufficiently Random Values

Java

import java.security.SecureRandom;

public class IdGenerator {
    private static final SecureRandom random = new SecureRandom();

    public static String generateId() {
        return Long.toHexString(random.nextLong());
    }
}

Node.js

const crypto = require('crypto');

function generateId() {
    return crypto.randomBytes(16).toString('hex');
}

console.log(generateId());

Python/Django

import secrets

def generate_id():
    return str(secrets.randbelow(1000))

print(generate_id())

PHP

<?php

function generate_id() {
    $random = random_bytes(16);
    return bin2hex($random);
}

echo generate_id();
?>

How to Ask AI to Check Your Code for Use of Insufficiently Random Values

Review the following [language] code block for potential CWE-330 Use of Insufficiently Random Values vulnerabilities and rewrite it using a well-vetted algorithm:

import random

def generate_id():
    return str(random.randint(1, 1000))

id = generate_id()
print(id)

Rewrite the above code using a well-vetted algorithm like secrets.randbelow():

import secrets

def generate_id():
    return str(secrets.randbelow(1000))

id = generate_id()
print(id)

Use of Insufficiently Random Values Best Practices Checklist

✅ Verify that all pseudo-random number generators (PRNGs) used in your product have adequate length seeds. ✅ Select well-tested implementations with adequate length seeds for all PRNGs. ✅ Consider using a PRNG that re-seeds itself as needed from high-quality pseudo-random output sources.

Use of Insufficiently Random Values FAQ

How do I identify a CWE-330 vulnerability?

A CWE-330 vulnerability occurs when a product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.

What are the common consequences of a CWE-330 vulnerability?

The common consequences of a CWE-330 vulnerability include confidentiality breaches, integrity violations, and availability disruptions.

How do I prevent CWE-330 vulnerabilities?

To prevent CWE-330 vulnerabilities, use well-vetted algorithms that are currently considered strong by experts in the field, select well-tested implementations with adequate length seeds, and consider a PRNG that re-seeds itself as needed from high-quality pseudo-random output sources.

What are some common mitigation strategies for CWE-330 vulnerabilities?

Some common mitigation strategies for CWE-330 vulnerabilities include using products or modules that conform to FIPS 140-2, consulting FIPS 140-2 Annex C, and re-seeding the PRNG as needed from high-quality pseudo-random output sources.

How do I detect CWE-330 vulnerabilities?

To detect CWE-330 vulnerabilities, use manual testing techniques such as reviewing code for insufficiently random numbers or values, using automated scanners to identify potential vulnerabilities, and leveraging PenScan’s detection capabilities.

What are some best practices for preventing CWE-330 vulnerabilities?

Some best practices for preventing CWE-330 vulnerabilities include verifying return values are correct, testing your code thoroughly, and using an allowlist of allowed values.

Vulnerabilities Related to Use of Insufficiently Random Values

References

• MITRE
• OWASP A04:2025 - Cryptographic Failures
• CAPEC-112, CAPEC-485, CAPEC-59
• NVD

Scan Your Own Site

Manual code review catches what you know to look for. An automated scan catches what you didn’t. Scan your own website using PenScan to find Use of Insufficiently Random Values and other risks before an attacker does.