CVE-2025-66264: Unquoted Service Path in CMService.exe Exploitable for Privilege Escalation

Overview

CVE-2025-66264 describes a critical vulnerability found in the CMService.exe service. This service, which runs with SYSTEM privileges, contains an unquoted service path. This flaw allows a local attacker with write access to the filesystem to potentially escalate their privileges to SYSTEM by injecting a malicious executable into a directory within the service’s path.

Technical Details

The vulnerability stems from the way the Windows operating system parses service paths that lack quotation marks. When a service path is not enclosed in quotes, Windows attempts to execute each space-separated segment of the path as a separate executable. For example, if the service path is C:\Program Files\Company Name\CMService.exe, Windows will first try to execute C:\Program, then C:\Program Files\Company, and so on.

If a standard user with write access can place a malicious executable named ‘Program.exe’ in the C:\ directory, the service will execute this malicious executable with SYSTEM privileges during startup. This grants the attacker full control over the system.

CVSS Analysis

Due to the nature of the provided information, a CVSS score is currently unavailable. However, this vulnerability is HIGHLY likely to be rated as HIGH severity. While it requires local access and write privileges, the ability to escalate to SYSTEM privileges makes it a significant risk.

Factors influencing the severity include:

• Attack Vector: Local
• Attack Complexity: Low (Given write access)
• Privileges Required: Low (Standard user with write access)
• User Interaction: None
• Scope: Changed (Privilege escalation from user to SYSTEM)
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

Possible Impact

Successful exploitation of CVE-2025-66264 can have severe consequences:

• Full System Compromise: An attacker gains complete control over the affected system.
• Data Theft: Sensitive data can be accessed and exfiltrated.
• Malware Installation: The attacker can install malware, including ransomware, backdoors, or keyloggers.
• System Disruption: The attacker can cause system crashes or render the system unusable.
• Lateral Movement: The compromised system can be used as a foothold to attack other systems on the network.

Mitigation and Patch Steps

The primary mitigation for CVE-2025-66264 is to ensure the service path for CMService.exe is properly quoted.

1. Apply the Patch: Check the vendor’s website (https://www.megatec.com.tw/software-download/) for a security patch or updated version of the software. Apply the patch as soon as possible.
2. Quote the Service Path: If a patch is not immediately available, you can manually modify the service path in the Windows Registry to include quotation marks around the entire path.
   • Open the Registry Editor (regedit.exe).
   • Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\CMService
   • Modify the ImagePath value to include quotes around the entire path. For example, change C:\Program Files\Company Name\CMService.exe to "C:\Program Files\Company Name\CMService.exe"
   • Restart the CMService service or the entire system for the changes to take effect.
3. Restrict Write Access: Restrict write access to directories in the service path to prevent unauthorized users from placing malicious executables.

References

Megatec Software Download Page