CVE-2024-7239

Executive Summary

CVE-2024-7239 is a local privilege escalation vulnerability in VIPRE Advanced Security, specifically within the Anti Malware Service. The flaw allows an attacker with low-privileged code execution on the target system to escalate privileges to SYSTEM by exploiting a symbolic link (symlink) following issue. By creating a malicious symlink, the attacker can abuse the service to delete arbitrary files, leading to privilege escalation and arbitrary code execution in the context of SYSTEM. The vulnerability has a CVSS score of 7.8 (High) and is currently unpatched. No public exploit code or proof-of-concept is available at this time.

CVSS Breakdown & Threat Level

• CVSS Score: 7.8 (High)
• Attack Vector: Local (AV:L)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)

The threat level is high due to the potential for complete system compromise from a low-privileged foothold. The attack complexity is low, requiring only the ability to execute low-privileged code and create a symbolic link.

Deep Dive & Mechanics

The vulnerability resides in the VIPRE Anti Malware Service, which runs with SYSTEM privileges. The service performs file operations (specifically file deletion) based on input that can be influenced by a local user. By creating a symbolic link (symlink) pointing to a critical system file (e.g., C:\Windows\System32\config\SAM), an attacker can trick the service into deleting that file instead of the intended target. This can lead to denial of service, data corruption, or, more critically, privilege escalation if the attacker can leverage the deletion to overwrite a file used for privilege escalation (e.g., a DLL loaded by a SYSTEM process).

The attack flow:

1. Attacker gains low-privileged code execution on the target system.
2. Attacker identifies a file path that the VIPRE Anti Malware Service will delete.
3. Attacker creates a symbolic link at that path, pointing to a target file (e.g., a system binary or a file used for privilege escalation).
4. The VIPRE service, running as SYSTEM, follows the symlink and deletes the target file.
5. Attacker exploits the deletion to escalate privileges (e.g., by replacing the deleted file with a malicious version).

Vulnerable vs. Patched Code

No patched version is available. The vulnerable code is within the VIPRE Anti Malware Service's file deletion routine. The service likely uses a function like DeleteFile or MoveFileEx without first verifying that the target path is not a symbolic link. A patched version would need to:

• Use CreateFile with the FILE_FLAG_OPEN_REPARSE_POINT flag to prevent following symlinks.
• Verify the final target path is within an allowed directory.
• Use NtDeleteFile with appropriate security checks.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Low-privileged access to a Windows system running VIPRE Advanced Security.
• Ability to create symbolic links (requires SeCreateSymbolicLinkPrivilege, which is often granted to standard users on Windows 10/11).

Exploitation Steps:

1. Identify a file path that VIPRE Anti Malware Service will delete. This may require reverse engineering or monitoring the service's behavior.
2. Create a symbolic link:

   mklink C:\path\to\vuln\file.txt C:\Windows\System32\config\SAM
   

3. Trigger the VIPRE service to delete the file (e.g., by initiating a scan or quarantine action).
4. After deletion, exploit the missing file to escalate privileges (e.g., by creating a hard link to a SYSTEM-owned file or using a known technique like sethc.exe backdoor).

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

Blue Team

Detection:

• Monitor for creation of symbolic links by non-administrator users, especially to sensitive system paths.
• Monitor for file deletion events on critical system files (e.g., SAM, SYSTEM, security logs).
• Use Sysmon Event ID 1 (Process creation) to detect mklink usage.
• Use Sysmon Event ID 11 (FileCreate) to detect symlink creation.

Hunting:

• Search for symbolic links pointing to C:\Windows\System32\config\* or other sensitive paths.
• Look for unusual file deletion patterns by the VIPRE Anti Malware Service.

Indicators of Compromise (IOCs)

• File Paths:
  • C:\Users\*\AppData\Local\Temp\*.lnk (malicious symlinks)
  • C:\Windows\System32\config\SAM (deleted or modified)
  • C:\Windows\System32\sethc.exe (deleted or replaced)
• Process Names:
  • Vipre* (VIPRE Anti Malware Service)
  • cmd.exe or powershell.exe creating symlinks
• Registry Keys:
  • HKLM\SYSTEM\CurrentControlSet\Services\Vipre* (service configuration)
• Network Indicators:
  • None specific to this vulnerability.

Detection Engineering

YARA Rule

rule CVE_2024_7239_Symlink_Abuse {
    meta:
        description = "Detects symbolic link creation targeting sensitive system paths"
        author = "Valters IT"
        date = "2025-01-01"
        reference = "CVE-2024-7239"
    strings:
        $symlink_cmd = "mklink" nocase
        $target_path = "\\Windows\\System32\\config\\" nocase
        $target_sam = "SAM" nocase
        $target_system = "SYSTEM" nocase
    condition:
        $symlink_cmd and ($target_path or $target_sam or $target_system)
}

Sigma Rule

title: CVE-2024-7239 - VIPRE Symlink Privilege Escalation
id: 7b8c9d0e-1f2a-3b4c-5d6e-7f8a9b0c1d2e
status: experimental
description: Detects creation of symbolic links to sensitive system paths, indicative of CVE-2024-7239 exploitation.
author: Valters IT
date: 2025-01-01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-7239
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains|all:
            - 'mklink'
            - 'Windows\System32\config'
    condition: selection
falsepositives:
    - Legitimate administrative tasks
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-7239 - VIPRE Symlink Exploit Attempt"; flow:to_server,established; content:"mklink"; nocase; content:"Windows\\System32\\config"; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict Symlink Creation: Disable the SeCreateSymbolicLinkPrivilege for standard users via Group Policy or Local Security Policy.
2. Monitor VIPRE Service: Use Sysmon or EDR to monitor file deletion events by the VIPRE Anti Malware Service.
3. Apply Least Privilege: Ensure users run with minimal privileges necessary.

Long-Term Fix:

• Await an official patch from VIPRE. In the meantime, consider using an alternative security solution if the risk is unacceptable.
• Implement application whitelisting to prevent unauthorized executables from running.

Workaround:

• If possible, disable the file deletion feature of the VIPRE Anti Malware Service until a patch is available.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert