Fragment and Forge: Breaking Wi-Fi Through Frame Aggregation and Fragmentation Mathy Vanhoef New York University Abu Dhabi
[email protected] Abstract These issues were discovered by analyzing open source Wi-Fi In this paper, we present three design flaws in the 802.11 stacks and systematically inspecting the 802.11 standard. Our standard that underpins Wi-Fi. One design flaw is in the frame results affect all protected Wi-Fi networks, including old net- aggregation functionality, and another two are in the frame works using Wired Equivalent Privacy (WEP), up to and in- fragmentation functionality. These design flaws enable an cluding the latest Wi-Fi Protected Access 3 (WPA3). Since adversary to forge encrypted frames in various ways, which in even WEP is affected, this implies the root cause of several turn enables exfiltration of sensitive data. We also discovered design flaws has been part of Wi-Fi since its release in 1997. common implementation flaws related to aggregation and Equally worrisome is that every single device we tested was fragmentation, which further worsen the impact of our attacks. vulnerable to at least one of our attacks. Our results affect all protected Wi-Fi networks, ranging from The most trivial design flaw is in 802.11’s frame aggrega- WEP all the way to WPA3, meaning the discovered flaws tion functionality: by flipping an unauthenticated flag in the have been part of Wi-Fi since its release in 1997. In our header of a frame, the encrypted payload will be parsed as experiments, all devices were vulnerable to one or more of our containing one or more aggregated frames instead of a nor- attacks, confirming that all Wi-Fi devices are likely affected.