lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [day] [month] [year] [list]
Date: Sun, 7 May 2017 07:32:37 +0000
From: Roee Hay <>
To: "" <>,
 "" <>
Subject: [FD] Aleph Research: Google Nexus 9 SensorHub Firmware Downgrade
 Vulnerability (CVE-2017-0582)

Google Nexus 9 SensorHub Firmware Downgrade Vulnerability


Google Nexus 9

Vulnerable Version:
Nexus 9 Android Builds before N4F27B - May 2017, i.e. before bootloader

Install N4F27B or later (bootloader version


Technical Details:
The Nexus 9 device contains a SoC manufactured by Cywee which implements a "Sensor Hub". The SoC is an STM32F401B/C ARM Cortext-M4 MCU, managed by a driver available under drivers/i2c/chips/CwMcuSensor.c. The platform communicates with SensorHub via I2C bus #0 and 4 GPIO ports.

Upon the platform boot, the CwMcuSensor driver queries the firmware's version (I2C register 0x10). If it does not match the one found in the vendor's partition (/vendor/firmware/sensor_hub.img), it switches to the bootloader mode, and upgrades the firmware (again, via I2C). Please note that the firmware is not signed.

By issuing a proprietary fastboot oem command: 'sensorhubflash', a physical attacker / malicious charger / malicious headphones (via the UART interface, exposed by the headphones jack - see our blog post [2]) can downgrade the SensorHub firmware to an old version, saved under the 'SER' partition (/dev/block/mmcblk0p19). This version may contain vulnerabilities which may allow the attacker to compromise the MCU.
One may claim that it is not an issue because the platform would immediately upgrade the firmware upon boot (since its version is different from the one found in the vendor image), however, in Nexus 9, the I2C buses could be accessed via the fastboot interface, by using the fastboot oem {i2cr, i2cw, i2crNoAddr, i2cwNoAddr, i2cdetect} commands. (I2C could also be accessed via UART, in the HBOOT mode. [2]) Thus, the attacker could interact with the old firmware BEFORE it was replaced by the platform using I2C, and thus potentially exploit a security vulnerability which would allow him to return a bogus version identifier, bypassing the platform's check. Please note that the SoC's I2C code runs in privileged mode.

For more details and PoC, visit the Aleph Research Vulnerability Report [1].

Google patched the vulnerability on build N4F27B / bootloader by removing the 'sensorhubflash' bootloader command. In addition, Google restricted access to the I2C buses - The I2C related bootloader commands are no longer available.
Please note that although Google published the advisory on the April 2017 Security Bulletin [3], the patch has been included only since the April 5 2017 Security Patch Level, where the April Nexus 9 image (N4F26X) has the April 1 2017 Security Patch Level, hence it does not contain the patched bootloader.

Roee Hay (@roeehay) of Aleph Research, HCL technologies.

[1] Aleph Research Vulnerability Report.
[2] Attacking Nexus 9 with Malicious Headphones.
[3] Google's Security Bulletin (April 2017).


The contents of this e-mail and any attachment(s) are confidential and intended for the named recipient(s) only.
E-mail transmission is not guaranteed to be secure or error-free as information could be intercepted, corrupted,
lost, destroyed, arrive late or incomplete, or may contain viruses in transmission. The e mail and its contents
(with or without referred errors) shall therefore not attach any liability on the originator or HCL or its affiliates.
Views or opinions, if any, presented in this email are solely those of the author and may not necessarily reflect the
views or opinions of HCL or its affiliates. Any form of reproduction, dissemination, copying, disclosure, modification,
distribution and / or publication of this message without the prior written consent of authorized representative of
HCL is strictly prohibited. If you have received this email in error please delete it and notify the sender immediately.
Before opening any email and/or attachments, please check them for viruses and other defects.


Sent through the Full Disclosure mailing list
Web Archives & RSS:

Powered by blists - more mailing lists