CVE-2023-32175

Executive Summary

CVE-2023-32175 is a local privilege escalation vulnerability in VIPRE Antivirus Plus, specifically within the Anti Malware Service. The flaw allows a local attacker, who already has low-privileged code execution on the target system, to create a symbolic link and abuse the service to write arbitrary files. This can be leveraged to escalate privileges to SYSTEM and execute arbitrary code. The vulnerability was reported via ZDI-CAN-18899. The CVSS score is 7.8 (High), and the EPSS score is 0.0%, indicating low exploitation likelihood in the wild at the time of analysis. No public exploit code or proof-of-concept is currently available.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Base Score: 7.8 (High)
• Attack Vector: Local (AV:L) – Requires physical or remote access to the system.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: Low (PR:L) – Attacker must have initial low-privileged access.
• User Interaction: None (UI:N) – No user action needed.
• Scope: Unchanged (S:U) – The vulnerable component and the impacted component are the same.
• Confidentiality Impact: High (C:H) – Full system compromise possible.
• Integrity Impact: High (I:H) – Arbitrary file write leads to code execution.
• Availability Impact: High (A:H) – System can be rendered unusable.

Threat Level: High. While the EPSS score is low, the impact is severe, allowing a local attacker to gain full SYSTEM privileges.

Deep Dive & Mechanics

The vulnerability resides in the VIPRE Anti Malware Service, which runs with SYSTEM privileges. The service performs file operations (e.g., creating, deleting, or moving files) without properly validating the target path. A local attacker can exploit this by creating a symbolic link (symlink) that points from a location the service writes to, to a critical system file (e.g., C:\Windows\System32\evil.dll). When the service performs its file operation, it follows the symlink and writes attacker-controlled content to the target location, leading to privilege escalation.

Attack Flow:

1. Attacker gains low-privileged code execution on the target (e.g., via malware or user compromise).
2. Attacker identifies a directory or file that the VIPRE Anti Malware Service writes to (e.g., quarantine folder, log directory).
3. Attacker creates a symbolic link from that writable location to a high-value target (e.g., a system DLL or executable).
4. The VIPRE service, running as SYSTEM, writes data to the symlink path, effectively writing to the target.
5. Attacker triggers execution of the modified file (e.g., by restarting a service or waiting for system reboot) to gain SYSTEM-level code execution.

Vulnerable vs. Patched Code

No official patch or source code is available for comparison. The vulnerability is a classic symlink following issue (CWE-59). A patched version would likely include:

• Proper validation of file paths before writing.
• Use of NtCreateFile with FILE_OPEN_REPARSE_POINT flag to avoid following symlinks.
• Checking that the target file is not a symlink or junction point.
• Running file operations in a secure directory that cannot be manipulated by low-privileged users.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Local low-privileged access to a Windows system running VIPRE Antivirus Plus.
• Knowledge of a writable path used by the VIPRE Anti Malware Service.

Exploitation Steps:

1. Identify the service's writable directory (e.g., C:\ProgramData\VIPRE\Quarantine).
2. Create a symbolic link:

   mklink /D C:\ProgramData\VIPRE\Quarantine\evil C:\Windows\System32
   

3. Wait for the VIPRE service to write a file to the quarantine folder (e.g., by triggering a scan or quarantine event).
4. The service writes to C:\Windows\System32\evil.dll (or another target).
5. Execute the malicious DLL via rundll32 or by replacing a system binary.

Note: No public exploit code is available. This is a theoretical exploitation path.

Blue Team (Detection & Prevention)

Detection:

• Monitor for creation of symbolic links by non-SYSTEM processes, especially in directories used by security software.
• Alert on file writes to critical system directories (e.g., C:\Windows\System32) by the VIPRE service.
• Use Sysmon Event ID 1 (Process creation) and Event ID 11 (FileCreate) to track suspicious activity.

Prevention:

• Apply the principle of least privilege to the VIPRE service (though it requires SYSTEM for its functions).
• Use Windows Defender Attack Surface Reduction (ASR) rules to block symbolic link creation from low-integrity processes.
• Enable Windows Defender Credential Guard and Device Guard to mitigate privilege escalation.

Indicators of Compromise (IOCs)

• File Paths:
  • C:\ProgramData\VIPRE\Quarantine\* (suspicious symlinks)
  • C:\Windows\System32\* (unexpected files written by VIPRE service)
• Process Names:
  • Vipre* (any VIPRE process writing to system directories)
• Registry Keys:
  • HKLM\SYSTEM\CurrentControlSet\Services\Vipre* (service configuration)
• Network: None (local vulnerability)
• Hashes: No known malicious files.

Detection Engineering

YARA Rule

rule CVE_2023_32175_Symlink_Abuse {
    meta:
        description = "Detects symbolic link creation targeting VIPRE directories"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-32175"
    strings:
        $symlink_cmd = "mklink" nocase
        $vipre_path = "VIPRE" nocase
        $system32 = "System32" nocase
    condition:
        $symlink_cmd and $vipre_path and $system32
}

Sigma Rule

title: CVE-2023-32175 VIPRE Symlink Privilege Escalation
id: 8a9b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects symbolic link creation to system directories by low-privileged processes, indicative of CVE-2023-32175 exploitation.
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\cmd.exe'
        CommandLine|contains|all:
            - 'mklink'
            - 'VIPRE'
            - 'System32'
    condition: selection
falsepositives:
    - Legitimate administrative tasks
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2023-32175 VIPRE Symlink Exploit Attempt"; flow:to_server; content:"mklink"; nocase; content:"VIPRE"; nocase; content:"System32"; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected systems if exploitation is suspected.
2. Restrict local user permissions to prevent low-privileged code execution.
3. Monitor VIPRE service logs for unusual file write operations.

Long-term Fix:

• Vendor Patch: Await an official patch from VIPRE. Contact VIPRE support for updates.
• Workaround: If possible, disable the vulnerable service component (e.g., quarantine feature) until a patch is available.
• Hardening: Enable Windows Defender ASR rules to block symbolic link creation from untrusted processes.

Detection: Deploy the provided YARA, Sigma, and Suricata rules to detect exploitation attempts.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Analyst