MQTT library in Arm Mbed OS 2017-11-02 Improper Input Validation Vulnerability

Summary

A denial-of-service issue was discovered in the MQTT library in Arm Mbed OS 2017-11-02. The function readMQTTLenString() is called by the function MQTTDeserialize_publish() to get the length and content of the MQTT topic name. In the function readMQTTLenString(), mqttstring->lenstring.len is a part of user input, which can be manipulated.

 

 

 

 

 

 

 

 

 

 

Credit:

The information has been provided by Vendor

The original article can be found at:https://github.com/ARMmbed/mbed-os/issues/11802

 


Details

An attacker can simply change it to a larger value to invalidate the if statement so that the statements inside the if statement are skipped, letting the value of mqttstring->lenstring.data default to zero. Later, curn is accessed, which points to mqttstring->lenstring.data.

On an Arm Cortex-M chip, the value at address 0x0 is actually the initialization value for the MSP register. It is highly dependent on the actual firmware. Therefore, the behavior of the program is unpredictable from this time on.

 

Vulnerable Systems:

MQTT library in Arm Mbed OS 2017-11-02

 

CVE Information:

CVE-2019-17210

 

Disclosure Timeline:
Published Date: 11/04/2019