CVE-2025-66265
📋 TL;DR
CMService.exe creates the C:\usr directory with insecure permissions, granting write access to all authenticated users. This allows attackers to replace configuration files or hijack DLLs to escalate privileges. Affects systems running vulnerable versions of CMService software.
💻 Affected Systems
- CMService software from Megatec
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise through privilege escalation to SYSTEM/Administrator via DLL hijacking or malicious configuration file execution.
Likely Case
Local authenticated users gain elevated privileges by planting malicious files in the insecure directory structure.
If Mitigated
Limited to authenticated users with local access; proper permissions would prevent unauthorized writes.
🎯 Exploit Status
Exploitation requires authenticated access and knowledge of directory structure; trivial for local attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.megatec.com.tw/software-download/
Restart Required: No
Instructions:
1. Check vendor website for updated version
2. Install any available patches
3. Verify directory permissions are corrected
🔧 Temporary Workarounds
Secure Directory Permissions
windowsManually set proper permissions on C:\usr directory to remove write access for authenticated users
icacls C:\usr /remove "Authenticated Users" /T
icacls C:\usr /inheritance:r
icacls C:\usr /grant "SYSTEM:(OI)(CI)F" "Administrators:(OI)(CI)F"
🧯 If You Can't Patch
- Monitor C:\usr directory for unauthorized file modifications
- Restrict local user access to systems running CMService
🔍 How to Verify
Check if Vulnerable:
Check if C:\usr directory exists and has write permissions for Authenticated Users: icacls C:\usrCheck Version:
Check CMService version through installed programs or vendor documentationVerify Fix Applied:
Verify Authenticated Users group has no write permissions: icacls C:\usr | findstr "Authenticated Users"📡 Detection & Monitoring
Log Indicators:
- File creation/modification events in C:\usr directory by non-admin users
- Process execution from C:\usr directory
Network Indicators:
- No direct network indicators - local privilege escalation
SIEM Query:
EventID=4663 OR EventID=4656 AND ObjectName LIKE 'C:\\usr%' AND SubjectUserName NOT IN ('SYSTEM', 'Administrators')