Crypto-JS is one of the most popular JavaScript libraries for cryptographic standards. It's everywhere—used in browsers, Node.js, and by hundreds of other open source and commercial projects. But a quiet flaw tracked as CVE-2023-46233 could make your passwords and secrets *far* easier to crack than you think.

In this post, we’ll break down what went wrong, show vulnerable code, explain the consequences, and show you how to fix it.

What is CVE-2023-46233?

- CVE-2023-46233 is a security bug in crypto-js that affects how it implements PBKDF2 (Password-Based Key Derivation Function 2).
- PBKDF2 is designed to make password cracking difficult by using many iterations (repetitive hashing), slowing down brute-force attacks.

Default iterations: 1 (should be 1,000 at minimum—and preferably much higher)

Result: Keys derived from passwords are up to 1,300,000 times *easier* to brute-force than the current industry standards.

Why is This So Dangerous?

A single iteration with the weak SHA1 hash means attackers can check password guesses *thousands to millions* of times faster than against properly configured PBKDF2.

- If someone uses the default CryptoJS.PBKDF2 to protect passwords and stores the outputs (as in user authentication systems), an attacker could break many users' passwords rapidly.
- If developers use PBKDF2 to derive cryptographic keys for encrypting files or generating signatures, the underlying secrets are barely protected at all.

Here’s how many developers use crypto-js PBKDF2, trusting the defaults

const CryptoJS = require("crypto-js");

const password = "supersecret";
const salt = CryptoJS.lib.WordArray.random(128/8);

const key = CryptoJS.PBKDF2(password, salt); // BAD: uses SHA1, 1 iteration

It only does one iteration for key derivation.

An attacker who gets the derived key or the salt could brute-force it almost instantly using GPU hardware or even a regular CPU.

How Should You Be Using Crypto-JS PBKDF2?

Until you can update to crypto-js v4.2. or higher, _always_ specify a strong hash and a large number of iterations:

const CryptoJS = require("crypto-js");

const password = "supersecret";
const salt = CryptoJS.lib.WordArray.random(128/8);

// GOOD: Use SHA256 and at least 250,000 iterations
const key = CryptoJS.PBKDF2(password, salt, {
  keySize: 256/32,               // 256-bit key
  iterations: 250000,            // 250,000 iterations or more
  hasher: CryptoJS.algo.SHA256   // Use SHA256 instead of SHA1
});

keySize: Length of the resulting key in words (256 bits here).

- iterations: More is better, though it makes login/slower for users—250,000 is reasonable for most apps today.

How Did This Happen?

- The PBKDF2 function was added in Crypto-JS before password-cracking hardware accelerated and SHA1 became broken.

You are vulnerable if

- You use *crypto-js* PBKDF2 in any version before 4.2. and didn’t set the iteration count and hash manually.

Fixes

1. Upgrade Crypto-JS to v4.2.+, which sets a safe default (PBKDF2(password, salt) now uses SHA256 and 250,000 iterations by default).
- Release notes

Manually set the hasher and iteration count every time (see above code snippet).

3. Rotate any keys/passwords generated using the weak settings. Old data is likely at risk.

Never use SHA1 or a single iteration

OWASP recommendation for password storage

Additional Reading and References

- CVE-2023-46233 on NVD
- Crypto-JS PBKDF2 documentation
- GitHub Security Advisory
- Password Hashing Competition winners

Final Thoughts

Crypto is _hard_ — but setting strong defaults is smart security. If your project uses crypto-js, check your PBKDF2 calls and the library version. This is one of those bugs (CVE-2023-46233) that sneaks into even careful codebases, so don’t assume you’re safe.

Stay safe!

*(Feel free to share and use the code snippets above to protect your own and your users’ passwords.)*

Timeline

Published on: 10/25/2023 21:15:10 UTC
Last modified on: 11/27/2023 20:15:06 UTC