CVE-2023-5447

Executive Summary

CVE-2023-5447 is a denial-of-service vulnerability in the Synaptics Hardware Support App (SynHsaService). The flaw is a use-after-free condition caused by a missing lock check, which can lead to abnormal termination of the service. This results in a local denial of service, requiring low privileges to exploit. The vulnerability has a CVSS score of 5.5 (Medium) and currently has no known public exploit or patch. The EPSS score is 0.0%, indicating a very low probability of exploitation in the wild.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a local service component of Synaptics hardware drivers, typically distributed through OEM channels or direct driver updates.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
• Base Score: 5.5 (Medium)
• Attack Vector: Local (AV:L) – The attacker must have local access to the system.
• Attack Complexity: Low (AC:L) – No special conditions are required.
• Privileges Required: Low (PR:L) – The attacker needs a standard user account.
• User Interaction: None (UI:N) – No user action is needed beyond the attacker’s own.
• Scope: Unchanged (S:U) – The vulnerability does not affect other components.
• Confidentiality Impact: None (C:N) – No data exposure.
• Integrity Impact: None (I:N) – No data modification.
• Availability Impact: High (A:H) – The service is terminated, causing denial of service.

Threat Level: Medium. The vulnerability is local and requires low privileges, but the impact is limited to denial of service. No public exploit exists, and the EPSS score is 0.0%.

Deep Dive & Mechanics

The vulnerability resides in the SynHsaService, a component of the Synaptics Hardware Support App. The service is responsible for managing hardware interactions, likely for touchpads or other input devices.

Root Cause: A missing lock check in the service’s code leads to a race condition. When multiple threads access shared memory or resources without proper synchronization, a use-after-free condition can occur. Specifically, one thread may free a memory object while another thread still holds a reference to it, leading to a dangling pointer.

Trigger: An attacker with local access can craft a sequence of operations (e.g., rapid API calls or IOCTL requests) that cause the service to free a resource while it is still in use. This results in a crash of the SynHsaService process.

Impact: The service terminates abnormally, and the Synaptics Hardware Support App becomes unavailable. This may cause the touchpad or other Synaptics hardware to stop functioning until the service is restarted or the system is rebooted.

Affected Component: SynHsaService (part of Synaptics Hardware Support App). The exact version range is unknown, but it likely affects versions prior to a fix that has not been publicly released.

Vulnerable vs. Patched Code

No official patch or code diff is available. However, the fix would involve adding proper lock synchronization (e.g., mutex or critical section) around the vulnerable code path to prevent concurrent access to freed memory.

Vulnerable Code (Conceptual):

// Missing lock check
void process_request(Request *req) {
    Resource *res = get_resource(req->id);
    if (res) {
        // Use resource
        use_resource(res);
        // Another thread may free res here
        free_resource(res); // Potential use-after-free
    }
}

Patched Code (Conceptual):

// With proper lock
void process_request(Request *req) {
    lock(mutex);
    Resource *res = get_resource(req->id);
    if (res) {
        use_resource(res);
        free_resource(res);
    }
    unlock(mutex);
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Local access to a Windows system with Synaptics Hardware Support App installed.
• Low-privilege user account.

Exploitation Steps:

1. Identify the SynHsaService process (e.g., via Task Manager or sc query).
2. Craft a script or program that sends a series of IOCTL or API calls to the service in a race condition pattern.
3. Execute the script to trigger the use-after-free, causing the service to crash.

Example PoC (Conceptual):

import ctypes
import threading

# Assume we have a handle to the service
def trigger_race():
    # Send IOCTL that frees a resource
    ctypes.windll.kernel32.DeviceIoControl(...)

def main():
    threads = []
    for _ in range(10):
        t = threading.Thread(target=trigger_race)
        threads.append(t)
        t.start()
    for t in threads:
        t.join()

if __name__ == "__main__":
    main()

Note: No public exploit code is available. The above is a conceptual example.

Blue Team (Detection & Defense)

Detection:

• Monitor for abnormal termination of SynHsaService (Event ID 7031 or 7034 in Windows Event Log).
• Look for repeated crashes of the service within a short time window.
• Use Sysmon to detect unusual process creation or API calls targeting the service.

Defense:

• Apply the latest Synaptics driver updates from the OEM.
• Restrict local user privileges to prevent exploitation.
• Enable Windows Defender Exploit Guard to mitigate use-after-free attacks.

Indicators of Compromise (IOCs)

• Process: SynHsaService.exe crashing repeatedly.
• Event Logs: Windows System Event Log with Event ID 7031 (Service terminated unexpectedly) or 7034 (Service crashed).
• File: No specific file IOCs; the vulnerability is in the service binary itself.
• Network: No network indicators; the attack is local.

Detection Engineering

YARA Rule

rule CVE_2023_5447_Synaptics_UseAfterFree {
    meta:
        description = "Detects potential exploitation of CVE-2023-5447 in SynHsaService"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-5447"
    strings:
        $s1 = "SynHsaService" nocase
        $s2 = "use-after-free" nocase
        $s3 = "missing lock" nocase
    condition:
        $s1 or $s2 or $s3
}

Sigma Rule

title: SynHsaService Crash Detection
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects abnormal termination of SynHsaService, indicating possible exploitation of CVE-2023-5447
author: Valters IT
date: 2025-04-10
logsource:
    product: windows
    service: system
detection:
    selection:
        EventID:
            - 7031
            - 7034
        ServiceName: 'SynHsaService'
    condition: selection
falsepositives:
    - Legitimate service crashes due to system instability
level: medium

Suricata Rule

alert ip any any -> any any (msg:"CVE-2023-5447 Synaptics Use-After-Free Exploitation Attempt"; content:"SynHsaService"; nocase; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Check for driver updates from the system OEM (e.g., Dell, HP, Lenovo) for Synaptics hardware.
2. If no update is available, consider disabling the Synaptics Hardware Support App if not required (via Services.msc).
3. Restrict local user accounts to standard privileges to reduce attack surface.

Long-Term Fix:

• Synaptics must release a patched version of the SynHsaService with proper lock synchronization.
• Monitor the Synaptics security advisory page for updates.

Workaround:

• Use Group Policy to prevent non-administrator users from interacting with the service.

Valters IT
DevSecOps & Cyber Threat Intelligence