CVE-2024-9157: Synaptics Audio Drivers Privilege Escalation

CVE-2024-9157 Overview

CVE-2024-9157 is a local privilege escalation vulnerability in the Synaptics audio driver services CxUIUSvc64.exe and CxUIUSvc32.exe. A locally authorized attacker can load an arbitrary DLL into a privileged process, gaining SYSTEM-level code execution. The affected product is End-of-Life and unsupported, meaning no security patches will be issued. The CVE was assigned to alert operators still running the product that it must be removed from their environments. The weakness maps to improper access control [CWE-284].

Critical Impact
Local attackers with valid credentials can achieve SYSTEM privileges through DLL loading in Synaptics audio driver services running on End-of-Life software with no available vendor patch.

Affected Products

Synaptics audio drivers containing CxUIUSvc64.exe
Synaptics audio drivers containing CxUIUSvc32.exe
Status: End-of-Life, unsupported when CVE was assigned

Discovery Timeline

2025-03-11 - Synaptics publishes Audio Driver Security Brief
2025-03-11 - CVE-2024-9157 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-9157

Vulnerability Analysis

The vulnerability resides in the Synaptics audio driver user-mode services CxUIUSvc64.exe (64-bit) and CxUIUSvc32.exe (32-bit). These services run with elevated privileges to support audio driver user interface functionality. A locally authenticated attacker can force the service to load an attacker-controlled DLL, causing the malicious code to execute in the security context of the privileged process.

Successful exploitation grants the attacker full read, write, and execution control over the host. The result is a low-to-high privilege pivot suitable for post-compromise persistence, credential theft, and endpoint tampering.

Root Cause

The root cause is improper access control [CWE-284] in the audio driver services. The services do not sufficiently validate the source, path, or integrity of DLLs they load. This class of flaw typically results from insecure library search order, weak file system permissions on service directories, or missing signature enforcement on loaded modules.

Attack Vector

Exploitation requires local access with valid, low-privilege credentials. No user interaction is needed once the attacker has a foothold on the endpoint. The attacker plants a crafted DLL in a location searched by the privileged service and triggers the load. The DLL then executes with the elevated token of CxUIUSvc64.exe or CxUIUSvc32.exe.

Because the affected product is End-of-Life, no verified proof-of-concept code has been published by the vendor. Technical details are limited to the Synaptics Audio Driver Security Brief.

// No verified public exploit code is available.
// Refer to the Synaptics Audio Driver Security Brief for vendor guidance.

Detection Methods for CVE-2024-9157

Indicators of Compromise

Presence of CxUIUSvc64.exe or CxUIUSvc32.exe on any endpoint, indicating the End-of-Life driver is still installed.
Unsigned or unexpected DLLs loaded by CxUIUSvc64.exe or CxUIUSvc32.exe at runtime.
New files written to directories in the service's DLL search path by non-administrative users.
Child processes spawned from the audio service that do not match a legitimate driver workflow.

Detection Strategies

Inventory endpoints for the Synaptics audio driver package and flag installations as risk items due to End-of-Life status.
Hunt for module load events where CxUIUSvc64.exe or CxUIUSvc32.exe loads a DLL outside standard system paths.
Alert on file writes to service installation directories originating from standard user accounts.
Correlate service-hosted DLL loads with subsequent token elevation or privileged process creation.

Monitoring Recommendations

Enable Sysmon Event ID 7 (Image Loaded) to capture DLL loads by the Synaptics audio services.
Monitor Windows Security Event ID 4688 for process creations descending from CxUIUSvc*.exe.
Track file creation events (Sysmon Event ID 11) in Synaptics driver directories.
Baseline expected DLL modules loaded by the audio service and alert on deviations.

How to Mitigate CVE-2024-9157

Immediate Actions Required

Uninstall the affected Synaptics audio driver from every managed endpoint because the product is End-of-Life and will not receive a fix.
Replace with a vendor-supplied or OEM-supported audio driver package that is still under active maintenance.
Restrict local logon rights on endpoints where the driver cannot be immediately removed to reduce the pool of potential attackers.
Audit file system permissions on the driver installation directory to remove write access for non-privileged users.

Patch Information

No patch is available. Synaptics assigned this CVE to signal that the affected audio driver is End-of-Life and must be removed rather than updated. Refer to the Synaptics Audio Driver Security Brief for vendor guidance.

Workarounds

Stop and disable the CxUIUSvc64 and CxUIUSvc32 services where the driver cannot be removed immediately.
Apply application control policies (for example, Windows Defender Application Control or AppLocker) to block DLL loads from user-writable directories by the audio service.
Enforce signed-code requirements for DLLs loaded by services running as SYSTEM.
Deploy endpoint monitoring to detect suspicious module loads and privilege transitions on hosts pending remediation.

bash

# Windows: stop and disable the vulnerable services (run as Administrator)
sc.exe stop CxUIUSvc64
sc.exe config CxUIUSvc64 start= disabled
sc.exe stop CxUIUSvc32
sc.exe config CxUIUSvc32 start= disabled

# Verify the services are stopped and disabled
sc.exe query CxUIUSvc64
sc.exe query CxUIUSvc32