Advisory ID: SYSS-2021-058 Product: Razer Synapse Manufacturer: Razer Inc. Affected Version(s): Versions prior to 3.7.0228.022817 Tested Version(s): 3.6.0920.091710, 3.6.1010.101113, 3.6.1018.101823, 3.6.1130.111217, 3.6.1201.111814, 3.7.0131.011810 Vulnerability Type: Improper Privilege Management (CWE-269) Risk Level: Critical Solution Status: Fixed Manufacturer Notification: 2021-10-18 Solution Date: 2022-03-07 Public Disclosure: 2022-03-23 CVE Reference: CVE-2021-44226 Authors of Advisory: Dr. Oliver Schwarz, SySS GmbH Matthias Deeg, SySS GmbH ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overview: Razer Synapse is an additional driver software for Razer gaming devices. The manufacturer describes the product as a "unified cloud-based hardware configuration tool" (see [1]). Due to an unsafe installation path and improper privilege management, the associated system service "Razer Synapse Service" is vulnerable to DLL hijacking. As a result, local Windows users can abuse the Razer driver installer to obtain administrative privileges on Windows. In order to exploit the vulnerability, the attacker needs physical access to the machine and needs to prepare the attack before Razer Synapse is installed along with a Razer driver. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Vulnerability Details: The attack scenario considers a Windows machine without any previous installation of any Razer device or software. The attacker has a local unprivileged Windows account, physical access to the machine, and a device which is either a Razer peripheral or able to pretend to be one (such as a Bash Bunny or a Raspberry Pi Zero). The attacker aims at executing code with full system privileges. The attack exploits the Razer Synapse Service which runs with elevated privileges. While the main binary of the service is stored in the protected location "C:\Program Files (x86)\Razer\Synapse3\Service", it dynamically loads libraries from "C:\ProgramData\Razer\Synapse3\Service\bin". Before the installation, standard users can write to this path, since "C:\ProgramData" is world-writable on a standard installation of Windows. The Synapse installation procedure changes access privileges, so that standard users cannot write to the path any longer. In addition, it removes any previous files in that location. Furthermore, upon service start, the location is checked for DLLs that do not originate from Razer. However, if the path is created before the driver installation, the creator remains owner of the object and can still change directory and file permissions. In particular, the creator can deny access for the SYSTEM user and grant access for the attacker's user. The attack consists of three phases: 1. Before the installation of the driver/Synapse, the attacker creates "C:\ProgramData\Razer\Synapse3\Service" and denies write-access for SYSTEM. 2. Afterwards, the attacker triggers the installation of Synapse. This can be done without any elevated privileges by plugging in a Razer device and following the installation procedure for Synapse, if device-specific co-installers are not disabled. Alternatively, a device such as Bash Bunny or a Raspberry Pi Zero can be used and pretend to be a Razer device. 3. After the installation of Synapse has finished, the attacker grants full access to "C:\ProgramData\Razer\Synapse3" for both the SYSTEM user and the own low-privileged user account. Afterwards, the attacker places a prepared set of DLLs into "C:\ProgramData\Razer\Synapse3\Service\bin" and restarts the Razer Synapse Service, typically, by restarting the machine. SySS GmbH chose the following set of DLLs for a proof of concept: * RzLightingEngine.dll from the original installation * RSy3_LightingEffects.dll from the original installation * userenv_orig.dll, a copy from the standard Windows DLL at "C:\Windows\SysWOW64\userenv.dll" * userenv.dll, a malicious 32-bit DLL that creates a new admin user and redirects to userenv_orig.dll otherwise The attack has been successfully tested for the following versions of Razer Synapse: * 3.6.0920.091710 * 3.6.1010.101113 * 3.6.1018.101823 * 3.6.1130.111217 * 3.6.1201.111814 A modified version of the exploit has been successfully tested against version 3.7.0131.011810. The attack has been successfully tested on the following versions of Windows: * Windows 10 Enterprise 20H2 19042.1237 * Windows 10 Pro 20H2 19042.1237 * Windows 10 Pro 21H1 19043.1237 * Windows 10 Pro 21H1 19043.1266 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Solution: Razer has published a patched version that will be deployed automatically upon driver installation on current Windows builds. To prevent similar attacks through other co-installers, system administrators can disable them by setting the following key in the Windows registry: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Device Installer\DisableCoInstallers = 1 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclosure Timeline: 2021-10-07: Vulnerability discovered 2021-10-11: Initial contact to Razer support 2021-10-18: Vulnerability reported to manufacturer 2022-01-18: First direct contact with developer team 2022-02-03: First fix attempt (3.7.0131.011810) announced to SySS GmbH 2022-03-07: Final fix (3.7.0228.022817) announced to SySS GmbH 2022-03-23: Public disclosure of vulnerability ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ References: [1] Product website for Razer Synapse 3 https://www2.razer.com/eu-en/synapse-3 [2] SySS Security Advisory SYSS-2021-058 https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2021-058.txt [3] SySS Responsible Disclosure Policy https://www.syss.de/en/responsible-disclosure-policy [4] SySS Proof of Concept Video https://www.youtube.com/watch?v=P75BtYcnZ-A ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Credits: This security vulnerability was found by Dr. Oliver Schwarz of SySS GmbH. E-Mail: oliver.schwarz@syss.de Public Key: https://www.syss.de/fileadmin/dokumente/PGPKeys/Oliver_Schwarz.asc Key ID: 0x9716294F1294280D Key Fingerprint: D452 B014 E992 2886 E799 6B43 9716 294F 1294 280D ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclaimer: 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 website. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Copyright: Creative Commons - Attribution (by) - Version 3.0 URL: http://creativecommons.org/licenses/by/3.0/deed.en