The value for
iterations: randomNumber is not supposed to be a random number. It's an iteration count that controls the cost of PBKDF2. It's supposed to be set as high as tolerable in the application, and the protection afforded by PBKDF2 against password search grows about linearly with that parameter. In the following I assume a high
iterations (say a baseline of a hundred thousand), and that
salt gets stored someway. I also assume it's used HMAC-SHA-1 (the default) or HMAC-SHA-256 (also common).
As far a we know, the main weakness in what's described is that it's possible to test a passphrase, by running generateKey, and then testing the corresponding key using a known AES cryptogram. Is that "without caring about the passphrase"? That's unclear to me.
Problem is, PBKDF2 can be run at very high speed by attackers using GPUs, FPGAs or ASICs. When
iterations is high (as it should), PBKDF2 is the bottleneck of
generateKey and password search. So adversaries can search passwords orders of magnitude faster than normal users using CryptoJS. From the standpoint of making password search hard, which is it's main goal in the question, PBKDF2 is thus among the worst possible use of spare CPU power for key stretching when it comes to powerful adversaries. Much better options ar Argon2, scrypt, or even bcrypt.
You decide if it's coincidental that the NIST formerly recommended PBKDF2, and still does not mandate using something better; like it formerly pushed Dual_EC_DRBG, with the obvious intention of allowing US intelligence to break this crypto. Hanlon's razor may apply, but I hold NIST scientists in higher esteem.