using web crypto to decrypt AES-CBC: Uncaught (in promise) Error

var key = 'aaaaaaaaaaaaaaaa'
var iv = 'bbbbbbbbbbbbbbbb';
var ciphertext = '10f42fd95857ed2775cfbc4b471bc213';

/*
// from https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/importKey#PKCS_8_import
function str2ab(str) {
    const buf = new ArrayBuffer(str.length);
    const bufView = new Uint8Array(buf);
    for (let i = 0, strLen = str.length; i < strLen; i++) {
        bufView[i] = str.charCodeAt(i);
    }
    return buf;
}
*/
function hex2ab(hex){
    return new Uint8Array(hex.match(/[\da-f]{2}/gi).map(function (h) {return parseInt(h, 16)}));
}

key = new TextEncoder().encode(key);
iv = new TextEncoder().encode(iv);
//ciphertext = str2ab(ciphertext);
ciphertext = hex2ab(ciphertext); // Fix: Replcae latin1 encoding with hex decoding

window.crypto.subtle.importKey(
    'raw',
    key,
    {
        name: 'AES-CBC'
    },
    true, // can the key be extracted using SubtleCrypto.exportKey() / SubtleCrypto.wrapKey()?
    ['decrypt'] // keyUsages
).then(function(key) {
    window.crypto.subtle.decrypt(
        {
            name: "AES-CBC",
            iv: iv
        },
        key,
        ciphertext
    ).then(function(plaintext) {
        console.log(new TextDecoder().decode(plaintext));
    })
});