Kr00k Wi-Fi Vulnerability Affected a Billion Devices

RSA Conference 2020 – San Francisco – A vulnerability in the way that two Wi-Fi chipsets handled network interruptions and encryption keys could have given attackers the ability to decrypt some of the network packets sent by more than a billion common wireless devices and routers — including those from Amazon, Apple, and Samsung, security firm ESET said at the RSA Conference on Wednesday.

Found in late 2018, the vulnerability — dubbed Kr00k and assigned CVE-2019-15126 — can force part of the wireless communication between devices to use all zeroes for the encryption key, allowing the attacker to eavesdrop on a limited amount of wireless data. The National Vulnerability Database assigned the vulnerability a base score of 3.1, which makes it low severity.

"If an attack is successful, several kilobytes of potentially sensitive information can be exposed," Miloš Čermák, the lead ESET researcher into the Kr00k vulnerability, said in a statement. "By repeatedly triggering disassociations, the attacker can capture a number of network packets with potentially sensitive data."

The vulnerability expands on research that ESET over the past 18 months on home Internet of Things devices. In October 2019, the company revealed that older Amazon Echoes and Kindles were vulnerable to the Key Reinstallation Attack, or KRACK — a 2-year-old issue that allows bad actors to perform a man-in-the-middle attack.

The latest attack affects far more devices — more than a billion, according to ESET, including older Amazon Echo devices and Kindles, Apple iPad mini 2, various older Apple iPhones, the Apple MacBook Air, and various Google Nexus smartphones. At least two models of the Samsung Galaxy are affected, as are Raspberry Pi 3 and the Xiaomi Redmi 3S.

In addition, Wi-Fi access points from Asus and Huawei are vulnerable as well, potentially leaving some device communication vulnerable if the hotspot base station remains vulnerable, ESET stated in its analysis of the issue.

"This greatly increases the attack surface, as an adversary can decrypt data that was transmitted by a vulnerable access point, which is often beyond your control, to your device, which doesn’t have to be vulnerable," Robert Lipovský, an ESET researcher working with the Kr00k vulnerability research team, said in a statement.

Related to the KRACK vulnerability discovered in 2017, the vulnerability affects both WPA2-Personal and WPA2-Enterprise protocols. ESET first reported the vulnerability to Amazon more than a year ago, and with further research, discovered in July 2019 that the Cypress Wi-Fi chipset was the source of the security issue. In August, the company confirmed that the widely used Broadcom Wi-Fi chipsets were vulnerable as well.

The attack abuses an implementation flaw in the chipsets. When a Wi-Fi connection is lost — either because the device moves to a different network or due to interference — the device is "disassociated" from the network. The problem for the affected chipsets is that disassociation causes the key to be zeroed out and then any buffered data will be sent using that key of all zeros. By repeated disassociating the device from the network, an attacker can capture several data frames.

"Kr00k manifests itself after Wi-Fi disassociations, which can happen naturally, for example due to a weak Wi-Fi signal, or may be manually triggered by an attacker," ESET's Čermák said.

For more than a year, ESET has worked with device makers to create a fix for the issue and patch devices. Most users should be safe, but they should check that their devices have the more recent software updates, the company said. Even though the source of the bug is in the Wi-Fi chipsets, their behavior can be modified through the firmware. Patches for all affected devices made by major manufacturers have been released, ESET stated.

"To protect yourself, as a user, make sure you have updated all your Wi-Fi capable devices, including phones, tablets, laptops, IoT smart devices, and Wi-Fi access points and routers, to the latest firmware version," Lipovský said.

The company urged device manufacturers that may not have patched their device to reach out to their chipset vendors for more information.

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