KRACK Attack.

A key reinstallation attack against WPA2 that forces nonce reuse in the four-way handshake, letting an attacker decrypt or replay Wi-Fi traffic. It belongs to the Attacks & Threats category of cybersecurity.

A key reinstallation attack against WPA2 that forces nonce reuse in the four-way handshake, letting an attacker decrypt or replay Wi-Fi traffic.

KRACK (Key Reinstallation Attack) was disclosed in 2017 by Mathy Vanhoef and Frank Piessens of KU Leuven. It exploits a logic flaw in the WPA2 four-way handshake: by blocking message 4 and replaying message 3, the attacker forces the client to reinstall an already-in-use session key, resetting packet nonces and replay counters. Reused nonces break the AES-CCMP or TKIP keystream, enabling decryption, replay, and in some cases injection of packets. The flaw affects nearly every Wi-Fi implementation; CVE-2017-13077 through CVE-2017-13088 cover the variants. Mitigation requires patched supplicants on both clients and access points; WPA3 was partly designed to remove the underlying weakness.

Defences for KRACK Attack typically combine technical controls and operational practices, as detailed in the full definition above.

Common alternative names include: Key Reinstallation Attack, WPA2 handshake attack.