An advisory from US CERT has been circulating for the last week about a protocol level flaw in WPA & WPA2. The advisory itself was:

US-CERT has become aware of several key management vulnerabilities in the 4-way handshake of the Wi-Fi Protected Access II (WPA2) security protocol. The impact of exploiting these vulnerabilities includes decryption, packet replay, TCP connection hijacking, HTTP content injection, and others. Note that as protocol-level issues, most or all correct implementations of the standard will be affected. The CERT/CC and the reporting researcher KU Leuven, will be publicly disclosing these vulnerabilities on 16 October 2017.

Details of the vulnerability have been released today, and paint a pretty horrifying picture. Ultimately this is an issue with a mechanism for dealing with lost packets during the initial 4-way key negotiation and the client’s behavior when they receive one of these packets after they’re session is already established.

Almost all WiFi devices out there are vulnerable to this attack and patches should be applied as soon as they are available. Some very quick and important notes I’d like to make available for people:

  • This is an active against clients
  • WPA & WPA2 both personal and enterprise are effected
  • The WiFi association key (your network’s passphrase) is safe, this attack breaks a per-client session key.
  • Assume all your traffic is being sent in plain text and can be manipulated by an attacker until you have patched.

If you have a VPN available to your client devices, having it active will protect your traffic from this attack.