CVE-2025-50173: Weak Authentication in Windows Installer Leads to Privilege Elevation

Overview

This blog post focuses on the vulnerability CVE-2025-50173, a significant risk to the security of Windows operating systems. It allows an authorized attacker to exploit weak authentication in the Windows Installer and elevate their privileges on the system. This vulnerability specifically targets Windows systems, potentially compromising the integrity, availability, and confidentiality of these systems if not addressed. The vulnerability’s significance is underscored by its CVSS severity score of 7.8, making it a high-risk issue for organizations that rely on Windows systems.

Vulnerability Summary

CVE ID: CVE-2025-50173
Severity: High (CVSS: 7.8)
Attack Vector: Local
Privileges Required: Low
User Interaction: Required
Impact: System compromise and potential data leakage

Affected Products

Product | Affected Versions

Windows Installer | All versions prior to the patch

How the Exploit Works

The exploit takes advantage of the weak authentication present in the Windows Installer. An attacker with authorized access to the system can manipulate the authentication process to grant themselves elevated privileges. This could provide the attacker with system-level access, giving them the ability to modify, delete, or exfiltrate sensitive data, install malicious software, or completely compromise the system.

Conceptual Example Code

The example below is a conceptual representation of how the vulnerability might be exploited. This is not an actual exploit code but a simplified representation to understand the underlying mechanism.

# Attacker with low-level access initiates the installation process
C:\> msiexec /i C:\path\to\malicious.msi
# Malicious installer bypasses weak authentication and elevates privilege
C:\> net user /add attacker password
C:\> net localgroup Administrators attacker /add

In the above example, a malicious installer (`malicious.msi`) is used to exploit the weak authentication. Once executed, the attacker adds a new user (`attacker`) with a password (`password`) and then adds this new user to the Administrators group, effectively elevating the attacker’s privilege to the system administrator level.

Mitigation and Recommendations

To protect against this vulnerability, users are advised to apply the vendor-supplied patch as soon as it becomes available. In the interim, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can be used to detect and block attempts to exploit this vulnerability. Regular audits of system logs should also be performed to identify any suspicious activity.
In the long term, organizations should consider implementing strong authentication methods and privilege management strategies to prevent unauthorized privilege escalation. Regular patching and system updates should also be part of the organization’s security strategy.