He who is harry newton said on Mon, 16 Oct 2017 06:33:13 +0000 (UTC):

It works by exploiting a four-way handshake that's used to establish a key
for encrypting traffic. During the third step, the key can be resent
multiple times. When it's resent in certain ways, a cryptographic nonce can
be reused in a way that completely undermines the encryption.

https://arstechnica.com/information-technology/2017/10/severe-flaw-in-wpa2-protocol-leaves-wi-fi-traffic-open-to-eavesdropping/

More links now that they published the paper on the attack a half hour ago.
https://www.krackattacks.com

Manufacturers apparently had 50 days to effect the fix:
Key Reinstallation Attacks: Forcing Nonce Reuse in WPA2
https://papers.mathyvanhoef.com/ccs2017.pdf

Updates in http://tinyurl.com/alt-internet-wireless