This newly discovered flaw exposes passwords, and allows an attacker to view data thought to be encrypted.

Manufacturers are rushing to fix this, but there are a lot of devices out there to patch.  Technical details are in the article below.

Serious flaw in WPA2 protocol lets attackers intercept passwords and much more

DAN GOODIN - 10/16/2017, 12:37 AM
https://arstechnica.com/information-technology/2017/10/severe-flaw-in-wpa2-protocol-leaves-wi-fi-traffic-open-to-eavesdropping/

"Researchers have disclosed a serious weakness in the WPA2 protocol that allows attackers within range of vulnerable device or access point to intercept passwords, e-mails, and other data presumed to be encrypted, and in some cases, to inject ransomware or other malicious content into a website a client is visiting.

The proof-of-concept exploit is called KRACK, short for Key Reinstallation Attacks. The research has been a closely guarded secret for weeks ahead of a coordinated disclosure that was scheduled for 8am Monday, East Coast time. A website disclosing the vulnerability said it affects the core WPA2 protocol itself and is effective against devices running Android, Linux, and OpenBSD, and to a lesser extent macOS and Windows, as well as MediaTek Linksys, and other types of devices. The site warned that attackers can exploit the flaw to decrypt a wealth of sensitive data that's normally encrypted by the nearly ubiquitous Wi-Fi encryption protocol.

"This can be abused to steal sensitive information such as credit card numbers, passwords, chat messages, emails, photos, and so on," researcher Mathy Vanhoef, of the Katholieke Universiteit Leuven in Belgium wrote. "The attack works against all modern protected Wi-Fi networks. Depending on the network configuration, it is also possible to inject and manipulate data. For example, an attacker might be able to inject ransomware or other malware into websites."
It shows the attacker decrypting all data the phone sends to the access point. The attack works by forcing the phone into reinstalling an all-zero encryption key, rather than the real key. This ability, which also works on Linux, makes the attack particularly effective on these platforms.

The site went on to warn that visiting only HTTPS-protected Web pages wasn't automatically a remedy against the attack, since many improperly configured sites can be forced into dropping encrypted HTTPS traffic and instead transmitting unencrypted HTTP data. In the video demonstration, the attacker uses a script known as SSLstrip to force the site match.com to downgrade a connection to HTTP. The attacker is then able to steal an account password when the Android device logs in.

"Although websites or apps may use HTTPS as an additional layer of protection, we warn that this extra protection can (still) be bypassed in a worrying number of situations," the researchers explained. "For example, HTTPS was previously bypassed in non-browser software, in Apple's iOS and OS X, in Android apps, in Android apps again, in banking apps, and even in VPN apps."

The researcher went on to say that the weakness allows attackers to target both vulnerable access points as well as vulnerable computers, smartphones and other types of connecting clients, albeit with differing levels of difficulty and effectiveness. Neither Windows nor iOS are believed to be vulnerable to the most severe attacks. Linux and Android appear to be more susceptible, because attackers can force network decryption on clients in seconds with little effort.

Vanhoef said clients can be patched to prevent attacks even when connected to vulnerable access points. Linux patches have been developed, but it's not immediately clear when they will become available for various distributions and for Android users. Patches are also available for some but not all Wi-Fi access points."