CVE-2020-37252: Realtek Audio Service Unquoted Service Path Privilege Escalation

Technical summary

CVE-2020-37252 is an unquoted service path vulnerability (CWE-428) affecting Realtek Audio Service 1.0.0.55's RtkAudioService64.exe. The service executable path lacks quotation marks in the Windows service registry entry. This permits privilege escalation through DLL/executable injection into parent directories of the legitimate service path. When the service initializes—either at startup or during a system reboot—Windows resolves the unquoted path and loads the attacker's payload with LocalSystem privileges, bypassing standard user-mode restrictions.

Business impact

Successful exploitation grants an attacker complete system compromise via privilege escalation from a local user context to LocalSystem. This enables persistent backdoor installation, credential theft, lateral movement to other systems on the network, and potential ransomware deployment. Organizations relying on Realtek audio drivers in workstations or embedded systems face elevated risk of data exfiltration, operational disruption, and compliance violations if audio systems are part of security-critical infrastructure.

Affected systems

Realtek Audio Service version 1.0.0.55 running on Windows systems where the service is installed and active. The vulnerability requires local system access, so it is most relevant to shared workstations, terminal servers, and multi-user environments. Systems with strict physical access controls and single-user deployments face lower immediate risk, though the attack surface expands in remote work or BYOD scenarios where local privilege escalation could compound other network threats.

Exploitability

Exploitation requires local access (Access Vector: Local) and basic privileges (Privilege Required: Low), with no user interaction needed. The attack is straightforward: identify the unquoted service path, drop a malicious executable with an appropriate name into a searchable directory, and wait for service startup or system reboot. No special exploitation tools or deep system knowledge is required. The CVSS 3.1 score of 7.8 (HIGH) reflects the low barrier to entry and high impact once successful.

Remediation

Update Realtek Audio Service to a patched version that correctly quotes the service executable path in the registry. Verify the fix by inspecting the ImagePath value in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RtkAudioService64 to confirm it is enclosed in quotation marks (e.g., "C:\Program Files\Realtek Audio\...\RtkAudioService64.exe"). As an interim control, restrict write access to the Program Files directory and parent directories where the service path resides using file system ACLs.

Patch guidance

Consult Realtek's official advisory and download center to identify the latest Audio Service version that resolves this vulnerability. Verify the patched version number against the vendor's official release notes. Apply updates through the Realtek audio driver package installer or Windows Device Manager. In enterprise environments, use WSUS, SCCM, or equivalent patch management tools to coordinate deployment and ensure the service is restarted after patching. Test the patch in a lab environment first, particularly on systems with custom audio configurations, to confirm no regression in audio functionality.

Detection guidance

Monitor the RtkAudioService64 service startup and reboot events in Event Viewer (System log). Check for unexpected executable files in the service's parent directories or in common search paths like C:\, C:\Program Files, and C:\Program Files (x86). Use file integrity monitoring (FIM) tools to alert on new or modified executables near the service path. Review Windows Security event logs for privilege escalation events tied to RtkAudioService64 execution. Automated scanning tools (e.g., Configuration Compliance Scanner) can verify the proper quoting of the ImagePath registry value across endpoints.

Why prioritize this

Although CVE-2020-37252 is not currently listed on CISA's Known Exploited Vulnerabilities (KEV) catalog, the combination of high CVSS score (7.8), low exploitation difficulty, local privilege escalation impact, and presence in widely distributed audio hardware makes it a priority for organizations with Realtek installations. Unquoted service paths are a well-understood attack class with long historical precedent, increasing the likelihood of weaponization even without public KEV inclusion. Remediation effort is typically minimal, making rapid patching a high-value security action.

Risk score, explained

The CVSS 3.1 score of 7.8 (HIGH) is driven by the high impact on confidentiality, integrity, and availability (C:H/I:H/A:H), combined with low attack complexity and minimal privilege requirements (AV:L/AC:L/PR:L/UI:N/S:U). The Local attack vector reflects the requirement for account access to the affected system, not network-based exploitation. The absence of user interaction (UI:N) means the attacker only needs to place a file and wait for the scheduled service restart—no social engineering or user-triggered action is necessary. Scope is unchanged (S:U), so the impact is limited to the affected system and does not extend to other systems via the vulnerability itself, though privilege escalation to LocalSystem significantly increases the attacker's capability for lateral movement.

Frequently asked questions