In summary an attacker can clone your existing wifi connection. After which point you will connect to the clone connection without knowing. The attack method will also remove any secure connection ( https – SSL ) . Let see you visit this live and vulnerable website http://www.artsandscraps.org/ . This site is a Joomla based website and you enter your login details at http://www.artsandscraps.org/administrator/ . The attacker can grab those details unecrypted because they have clone your wifi connection. The website owner should force all web traffic to https://www.artsandscraps.org/administrator/ . which is a secure connect and encrypted. Here is the downside. The website owner is allowing secure and unsecure connection which puts you the user at risk.
We will documents some work around and ways you can protect yourself. Keep in mind the attacker do not need your wifi key for this to work.
From the searchers who discovered the vulnerability . krackattacks.com
As a proof-of-concept we executed a key reinstallation attack against an Android smartphone. In this demonstration, the attacker is able to decrypt all data that the victim transmits. For an attacker this is easy to accomplish, because our key reinstallation attack is exceptionally devastating against Linux and Android 6.0 or higher. This is because Android and Linux can be tricked into (re)installing an all-zero encryption key (see below for more info). When attacking other devices, it is harder to decrypt all packets, although a large number of packets can nevertheless be decrypted. In any case, the following demonstration highlights the type of information that an attacker can obtain when performing key reinstallation attacks against protected Wi-Fi networks:
Additional reading arstechnica.com