Crypto.decipher.final for 'aes-256-cbc' algorithm with invalid key fails with bad decrypt

I am able to use use node.js Crypto module to encrypt and decrypt a message using Cipher and Decipher classes with 'aes-256-cbc' algorithm like so:

var crypto = require('crypto');

var cipherKey = crypto.randomBytes(32); // aes-256 => key length is 256 bits => 32 bytes
var cipherIV = crypto.randomBytes(16); // aes block size = initialization vector size = 128 bits => 16 bytes
var cipher = crypto.createCipheriv('aes-256-cbc', cipherKey, cipherIV);

var message = 'Hello world';
var encrypted = cipher.update(message, 'utf8', 'hex') + cipher.final('hex');
console.log('Encrypted \'' + message + '\' as \'' + encrypted + '\' with key \''+ cipherKey.toString('hex') + '\' and IV \'' + cipherIV.toString('hex') + '\'');
// Outputs: Encrypted 'Hello world' as '2b8559ce4227c3c3c200ea126cb50957' with key '50f7a656cfa3c4f90796a972b2f6eedf41b589da705fdec95b9d25c180c16cf0' and IV '6b28c13d63af14cf05059a2a2caf370c'

var decipher = crypto.createDecipheriv('aes-256-cbc', cipherKey, cipherIV);
var decrypted = decipher.update(encrypted, 'hex', 'utf8') + decipher.final('utf8');
console.log('Decrypted \'' + encrypted + '\' as \'' + decrypted + '\' with key \''+ cipherKey.toString('hex') + '\' and IV \'' + cipherIV.toString('hex') + '\'');
// Outputs: Decrypted '2b8559ce4227c3c3c200ea126cb50957' as 'Hello world' with key '50f7a656cfa3c4f90796a972b2f6eedf41b589da705fdec95b9d25c180c16cf0' and IV '6b28c13d63af14cf05059a2a2caf370c'

However when I try to decrypt the message using a wrong key to, perhaps naively, demonstrate an attacker will not be able decrypt the message unless the key is known, I get Error: error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt at Decipheriv.final (internal/crypto/cipher.js:164:28):

var differentCipherKey = crypto.randomBytes(32);
var decipherDifferentKey = crypto.createDecipheriv('aes-256-cbc', differentCipherKey, cipherIV);
decrypted = decipherDifferentKey.update(encrypted, 'hex', 'utf8') + decipherDifferentKey.final('utf8');

What was I was hoping to get is unintelligible text. bad decrypt was featured in other SO questions either regarding openssl version mismatch between encrypting and decrypting or too-short initialization vector in the same case but I believe my case is a different scenario. Does AES somehow known that encrypted text was generated with a different key?

Tested on node v12.13.0 on Windows 10 and also in repl.it running v10.16.0.

EDIT: As suggested in the answers the issue was with default padding, in order to see unintelligible output one needs to disable auto-padding on both cipher and deciphers and pad manually:

var requirePadding = 16 - Buffer.byteLength(message, 'utf8');
var paddedMessage = Buffer.alloc(requirePadding, 0).toString('utf8') + message;
cipher.setAutoPadding(false)

Full example here

Solution

Another answer has correctly identified the issue as a padding problem. I might summarize the issue like so:

Block ciphers can only operate on data that has a length that is a multiple of the cipher's block size. (AES has a block size of 128 bits.)
In order to make variously-sized inputs conform to the block size, the library adds padding. This padding has a particular format (For example, when adding padding of length N, repeat the value N for the last N bytes of the input.)
When decrypting, the library checks that correct padding exists. Since your badly-decrypted data is arbitrary noise, it is very unlikely to have a valid pad.

You may turn this check off with decipher.setAutoPadding(false) before you do update. However, note that this will include the padding in your decrypted output. Here is a modified repl.it instance that uses setAutoPadding.