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Date: Thu, 10 Oct 2019 07:08:30 GMT
Subject: [SYSS-2019-035]: Microsoft Surface Mouse - Insufficient
 Protection of Code (Firmware) and Data (Cryptographic Key)

Hash: SHA512

Advisory ID: SYSS-2019-035
Product: Surface Mouse
Manufacturer: Microsoft
Affected Version(s): WS3-00002
Tested Version(s): WS3-00002
Vulnerability Type: Insufficient Protection of Code (Firmware) and 
                    Data (Cryptographic Key)
Risk Level: Medium
Solution Status: Open
Manufacturer Notification: 2019-07-31
Solution Date: -
Public Disclosure: 2019-10-10
CVE Reference: Not assigned yet
Author of Advisory: Matthias Deeg (SySS GmbH)



Microsoft Surface Mouse is a Bluetooth Low Energy (LE) mouse.

The manufacturer describes the product as follows (see [1]):

"Sculpted for your hand and designed for an elegantly simple work space,
Mouse is the perfect partner to your docked Surface and Keyboard. It was
designed to match the sleek aesthetic and exceptional performance of
your Surface. The metal scroll wheel feels solid under your finger,
and the shape of the body fits perfectly in your hand."

Due to the insufficient protection of the flash memory of the mouse, an
attacker with physical access has read and write access to the firmware
and the used cryptographic key.


Vulnerability Details:

SySS GmbH found out that the embedded flash memory of the Bluetooth LE
Microsoft Surface Mouse can be read and written via the SWD (Serial Wire
Debug) interface of the used nRF51822 Bluetooth SoC [2] as the flash
memory is not protected by the offered readback protection feature.

Thus, an attacker with physical access to the mouse can simply read and
write the nRF51822 flash memory contents and either extract the
cryptographic key (Bluetooth LE Long Term Key), for instance to perform
further attacks against the wireless communication, or modify the

However, even if the readback protection of the nRF51822 was enabled,
an attacker would be able to read and write the flash memory contents by
bypassing the security feature as described in [3] and [4] with
slightly more effort.


Proof of Concept (PoC):

SySS GmbH could successfully read the nRF51822 flash memory contents of
the Microsoft Surface Mouse via the SWD interface using a SEGGER J-Link
PRO [5] debug probe in combination with SEGGER J-Link Commander and
extract the currently used cryptographic key (Long Term Key).



According to Microsoft, the reported security issue does not meet
the bar for servicing via a security update [6].

The described security issue may be fixed in future versions of the


Disclosure Timeline:

2019-07-31: Vulnerability reported to manufacturer
2019-08-01: Microsoft confirms receipt of security advisory
2019-08-06: Microsoft responds that the reported issue does not meet
            the bar for servicing via a security update
2019-10-10: Public release of SySS security advisory



[1] Product website for Microsoft Surface Mouse
[2] nRF51822 Product Specification v3.1  
[3] Kris Brosch, Include Security, Firmware dumping technique for an ARM Cortex-M0 SoC, 2015
[4] Andrew Tierney, Pen Test Partners, NRF51822 code readout protection bypass - a how-to, 2018
[5] Product website for Segger J-Link PRO
[6] Microsoft Vulnerability Severity Classification for Windows
[7] SySS Security Advisory SYSS-2019-035
[8] SySS GmbH, SySS Responsible Disclosure Policy



This security vulnerability was found by Matthias Deeg of SySS GmbH.

E-Mail: matthias.deeg (at)
Public Key:
Key fingerprint = D1F0 A035 F06C E675 CDB9 0514 D9A4 BF6A 34AD 4DAB



The information provided in this security advisory is provided "as is"
and without warranty of any kind. Details of this security advisory may
be updated in order to provide as accurate information as possible. The
latest version of this security advisory is available on the SySS Web



Creative Commons - Attribution (by) - Version 3.0



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