Wireless network security has come a long way since the days of easily breakable Wired Equivalent Privacy (WEP). WiFi Protected Access (WPA) 2 has been the most commonly used standard since it was released in 2004 and has had very few vulnerabilities since the original release.
This week however researchers from ESET released the details of a new attack called Kr00k, which affects millions of devices all over the world. This vulnerability can allow an attacker to read data between the device and access point as if there was no encryption at all.
As detailed in a previous blog, device manufacturers rarely implement common standards like Bluetooth of WiFi into their products from scratch. They instead purchase and integrate one of
the many off the shelf solutions provided by Broadcom or others, tweaking for their specific use case.
The two most popular chipsets for WiFi come from Broadcom and Cypress, both of which are vulnerable to the Kr00k attack. These chipsets are used in millions of devices including smartphones, laptops, IoT devices, etc. This means that the attacks spans nearly every manufacturer of electronics
that uses WiFi in their products.
The attack itself is based on a bug in the access point disassociation logic. Disassociations happen via special control frames in a WiFi connection and happen all the time legitimately, whether from low signal or an intentional disconnect from an access point. When a disassociation request happens the vulnerable chipsets reset the transmit buffer with an encryption key of all zeros. This buffer is then finalized by being transmitted out using the all zero encryption key which makes it vulnerable to sniffing by a 3rd party. The transmit buffer is relatively small at only 32 kilobytes but using the attack sequentially via a script makes it possible to leak larger pieces of data given enough time. The same attack can also be used on the access point itself and is not limited to attacking a single client only.
By using the attack on a vulnerable access point it would be possible to eavesdrop on any client connected to the wireless net-work, whether it has already been patched or not.
After ESET researchers found the bug they responsibly disclosed it to the chipset makers and began a 120-day countdown for public disclosure. This gave manufacturers plenty of time to create a patch and start rolling it out to vulnerable devices. To make sure that your network is not vulnerable each device utilizing WiFi should be checked to make sure it is patched and up to date. It would also be wise to utilize VPN software when on untrusted networks as it may not be possible to verify that the access point is not vulnerable.