Espressif IoT devices susceptible to WiFi vulnerabilities can allow hijackers to crash devices connected to enterprise networks

Matheus Eduardo Garbelini a member of the ASSET (Automated Systems SEcuriTy) Research Group at the Singapore University of Technology and Design released a proof of concept for three WiFi vulnerabilities in the Espressif IoT devices, ESP32/ESP8266.

3 WiFi vulnerabilities on the ESP32/8266 IoT device

Zero PMK Installation (CVE-2019-12587)

This WiFi vulnerability hijacks clients on version ESP32 and ESP8266 connected to enterprise networks. It allows an attacker to take control of the WiFi device EAP session by sending an EAP-Fail message in the final step during the connection between the device and the access point.

The researcher discovered that both the IoT devices update their Pairwise Master Key (PMK) only when they receive an EAP-Success message. If the EAP-Fail message is received before the EAP-Success, the device skips to update the PMK received during a normal EAP exchange (EAP-PEAP, EAP-TTLS or EAP-TLS). During this time, the device normally accepts the EAPoL 4-Way handshake.

Each time ESP32/ESP8266 starts, the PMK is initialized as zero, thus, if an EAP-Fail message is sent before the EAP-Success, the device uses a zero PMK. Thus allowing the attacker to hijack the connection between the AP and the device.

ESP32/ESP8266 EAP client crash (CVE-2019-12586)

This WiFi vulnerability is found in SDKs of ESP32 and ESP8266 and allows an attacker to precisely cause a crash in any ESP32/ESP8266 connected to an enterprise network. In combination with the zero PMK Installation vulnerability, it could increase the damages to any unpatched device.

This vulnerability allows attackers in radio range to trigger a crash to any ESP device connected to an enterprise network. Espressif has fixed such a problem and committed patches for ESP32 SDK, however, the SDK and Arduino board support for ESP8266 is still unpatched.

ESP8266 Beacon Frame Crash (CVE-2019-12588)

In this WiFi vulnerability, CVE-2019-12588 the client 802.11 MAC implementation in Espressif ESP8266 NONOS SDK 3.0 and earlier does not correctly validate the RSN AuthKey suite list count in beacon frames, probe responses, and association responses. This allows attackers in radio range to cause a denial of service (crash) via a crafted message.

Two situations in a malformed beacon frame can trigger two problems:

When sending crafted 802.11 frames with the field Auth Key Management Suite Count (AKM) in RSN tag with size too large or incorrect, ESP8266 in station mode crashes.

When sending crafted 802.11 frames with the field Pairwise Cipher Suite Count in RSN tag with size too large or incorrect, ESP8266 in station mode crashes.

“The attacker sends a malformed beacon or probe response to an ESP8266 which is already connected to an access point. However, it was found that ESP8266 can crash even when there’s no connection to an AP, that is even when ESP8266 is just scanning for the AP,” the researcher says.

A user on Hacker News writes, “Due to cheap price ($2—$5 depending on the model) and very low barrier to entry technically, these devices are both very popular as well as very widespread in those two categories. These chips are the first hits for searches such as "Arduino wifi module", "breadboard wifi", "IoT wifi module", and many, many more as they're the downright easiest way to add wifi to something that doesn't have it out of the box.

I'm not sure how applicable these attack vectors are in the real world, but they affect a very large number of devices for sure.”

To know more about this news in detail, read the Proof of Concept on GitHub.