UPSilon 2000 Under Attack: Critical Privilege Escalation Vulnerability (CVE-2025-66266)

Overview

CVE-2025-66266 identifies a significant security vulnerability within UPSilon 2000, a UPS (Uninterruptible Power Supply) monitoring software. Specifically, the RupsMon.exe service executable suffers from insecure file permissions. The ‘Everyone’ group is granted ‘Full Control’ access to this executable, creating a pathway for local attackers to escalate their privileges to SYSTEM.

Technical Details

The root cause of this vulnerability lies in the overly permissive file permissions assigned to RupsMon.exe. With ‘Everyone’ granted ‘Full Control’, a local attacker can exploit this in several ways:

• Executable Replacement: An attacker can replace the legitimate RupsMon.exe with a malicious binary. When the service restarts (either automatically or manually), the attacker’s code will execute with SYSTEM privileges.
• Configuration Manipulation: An attacker might be able to modify the service’s configuration file (if accessible) to point to a command or script they control. Upon service start or stop (often triggered by UPS events), this malicious command/script would execute with SYSTEM privileges.

This exploit requires local access to the affected system.

CVSS Analysis

While the CVSS score is currently unavailable, given the potential for local privilege escalation to SYSTEM, this vulnerability is likely to be rated as High or Critical once assessed. A high CVSS score is anticipated due to the low attack complexity (requiring only local access and knowledge of the vulnerable service) and the significant impact on system integrity and confidentiality.

Possible Impact

Successful exploitation of CVE-2025-66266 can have severe consequences:

• Full System Compromise: An attacker gains complete control over the affected system with SYSTEM privileges.
• Data Theft: Sensitive data can be accessed, exfiltrated, or modified.
• Malware Installation: The system can be used as a foothold to install malware and spread to other systems on the network.
• Denial of Service: The system can be rendered unusable, disrupting critical operations.

Mitigation and Patch Steps

The following steps are recommended to mitigate this vulnerability:

1. Apply the Patch: Immediately apply the security patch provided by Megatec. This is the primary and most effective way to address the vulnerability. Check the vendor’s website for the patch.
2. Restrict File Permissions: As a temporary workaround (until a patch is available), restrict file permissions on RupsMon.exe. Remove ‘Full Control’ access for the ‘Everyone’ group and grant only necessary permissions to the appropriate user accounts or groups (e.g., the user account under which the UPSilon 2000 service runs).
3. Monitor Service Activity: Implement monitoring to detect any unauthorized modifications to RupsMon.exe or its configuration files.
4. Least Privilege Principle: Ensure all services and applications are running with the minimum necessary privileges.

References

Megatec Software Download Page