Razer Synapse 3.6.x DLL Hijacking

Razer Synapse versions prior to 3.7.0228.022817 suffer from a dll hijacking vulnerability.

MD5 | 1985d9f6a0035f77c5e0ebe58a378a00

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,
3.6.1130.111217, 3.6.1201.111814,
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



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
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

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
* 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 10 Enterprise 20H2 19042.1237
* Windows 10 Pro 20H2 19042.1237
* Windows 10 Pro 21H1 19043.1237
* Windows 10 Pro 21H1 19043.1266



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:

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



[1] Product website for Razer Synapse 3
[2] SySS Security Advisory SYSS-2021-058

[3] SySS Responsible Disclosure Policy
[4] SySS Proof of Concept Video



This security vulnerability was found by Dr. Oliver Schwarz of SySS GmbH.

E-Mail: [email protected]
Public Key:
Key ID: 0x9716294F1294280D
Key Fingerprint: D452 B014 E992 2886 E799 6B43 9716 294F 1294 280D



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.



Creative Commons - Attribution (by) - Version 3.0
URL: http://creativecommons.org/licenses/by/3.0/deed.en

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