CVE-2024-5928

Executive Summary

CVE-2024-5928 is a local privilege escalation vulnerability in VIPRE Advanced Security, specifically within the Patch Management Agent (PMAgent). The flaw allows a local attacker, who already has low-privileged code execution on the target system, to escalate privileges to SYSTEM by abusing an insecure link following behavior. By creating a symbolic link, an attacker can force the agent to delete a critical system file, 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 proof-of-concept or exploit code has been released, but the risk is significant for enterprise environments using VIPRE Advanced Security.

CVSS Breakdown & Threat Level

• CVSS Score: 7.8 (High)
• Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Local (AV:L) – The attacker must have local access to the system.
• Attack Complexity: Low (AC:L) – No special conditions are required beyond standard user privileges.
• Privileges Required: Low (PR:L) – The attacker needs low-privileged code execution.
• User Interaction: None (UI:N) – No user action is required.
• Scope: Unchanged (S:U) – The vulnerability does not cross trust boundaries.
• Confidentiality Impact: High (C:H) – Full system compromise possible.
• Integrity Impact: High (I:H) – Arbitrary file deletion and code execution.
• Availability Impact: High (A:H) – System instability or denial of service.

Threat Level: High. The vulnerability is locally exploitable with low privileges, and the impact is full SYSTEM-level compromise. The lack of a patch increases the risk for organizations using VIPRE Advanced Security.

Deep Dive & Mechanics

The vulnerability resides in the Patch Management Agent (PMAgent) component of VIPRE Advanced Security. The agent performs file operations (specifically file deletion) without properly validating the target path. By creating a symbolic link (symlink) from a location the agent accesses to a critical system file (e.g., C:\Windows\System32\config\SAM), an attacker can trick the agent into deleting that file.

Technical Details:

• The PMAgent runs with SYSTEM privileges.
• It performs file deletion operations based on internal logic (e.g., cleaning up temporary files or patch artifacts).
• The agent does not check whether the target path is a symlink or a junction point.
• An attacker with low-privileged access can create a symlink in a directory the agent monitors (e.g., C:\ProgramData\VIPRE\Temp).
• When the agent attempts to delete a file in that directory, it follows the symlink and deletes the target file instead.
• Deleting a critical system file (e.g., SAM, SYSTEM, or SECURITY hive) can cause system instability or allow the attacker to replace it with a malicious version, leading to privilege escalation.

Attack Flow:

1. Attacker gains low-privileged code execution (e.g., via phishing or another vulnerability).
2. Attacker identifies a directory where the PMAgent performs file deletions (e.g., C:\ProgramData\VIPRE\Temp).
3. Attacker creates a symlink named target_file.tmp pointing to C:\Windows\System32\config\SAM.
4. The PMAgent, running as SYSTEM, deletes target_file.tmp, which actually deletes the SAM hive.
5. The system becomes unstable or the attacker can exploit the missing SAM hive to gain SYSTEM privileges.

Vulnerable vs. Patched Code

Since no patch is available, a comparison is not possible. However, the vulnerable code likely resembles:

// Vulnerable pseudo-code
void DeleteFileInTempDir() {
    char path[MAX_PATH];
    GetTempPath(MAX_PATH, path);
    strcat(path, "\\VIPRE\\Temp\\patch_cleanup.tmp");
    DeleteFile(path);  // No symlink check
}

A patched version would include:

// Patched pseudo-code
void DeleteFileInTempDir() {
    char path[MAX_PATH];
    GetTempPath(MAX_PATH, path);
    strcat(path, "\\VIPRE\\Temp\\patch_cleanup.tmp");
    // Check if path is a symlink
    if (IsSymlink(path)) {
        LogError("Symlink detected, aborting deletion");
        return;
    }
    DeleteFile(path);
}

Exploitation & Lab Setup

Red Team

Lab Environment:

• Windows 10/11 VM with VIPRE Advanced Security installed (vulnerable version).
• Low-privileged user account.

Exploitation Steps:

1. Log in as a low-privileged user.
2. Identify the PMAgent's working directory (e.g., C:\ProgramData\VIPRE\Temp).
3. Create a symbolic link:

   mklink C:\ProgramData\VIPRE\Temp\patch_cleanup.tmp C:\Windows\System32\config\SAM
   

4. Trigger the PMAgent's file deletion operation (e.g., by initiating a patch scan or waiting for a scheduled task).
5. Observe that the SAM hive is deleted, causing system instability or allowing further exploitation.

Note: No public exploit code is available. The above steps are theoretical based on the vulnerability description.

Blue Team

Detection:

• Monitor for symlink creation events in directories used by VIPRE (e.g., C:\ProgramData\VIPRE\Temp).
• Alert on file deletion operations targeting critical system files (e.g., SAM, SYSTEM, SECURITY).
• Use Sysmon Event ID 1 (Process Creation) to detect mklink usage by non-administrative users.

Mitigation:

• Restrict write permissions to directories used by VIPRE to only SYSTEM and Administrators.
• Implement application whitelisting to block mklink execution for low-privileged users.
• Monitor for unusual file deletion patterns in C:\Windows\System32\config\.

Indicators of Compromise (IOCs)

• File Paths:

  • C:\ProgramData\VIPRE\Temp\*.tmp (symlink targets)
  • C:\Windows\System32\config\SAM (deleted or modified)
  • C:\Windows\System32\config\SYSTEM
  • C:\Windows\System32\config\SECURITY

• Process Names:

  • PMAgent.exe (VIPRE Patch Management Agent)
  • cmd.exe or powershell.exe executing mklink

• Registry Keys:

  • HKLM\SYSTEM\CurrentControlSet\Services\VIPRE\PMAgent (configuration)

• Network Indicators:

  • Outbound connections from VIPRE processes to update servers (normal behavior, but anomalous patterns may indicate exploitation).

Detection Engineering

YARA Rule

rule CVE_2024_5928_Symlink_Abuse {
    meta:
        description = "Detects symlink creation targeting VIPRE PMAgent directories"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-5928"
    strings:
        $s1 = "mklink" nocase
        $s2 = "VIPRE" nocase
        $s3 = "Temp" nocase
        $s4 = "\\System32\\config\\" nocase
    condition:
        all of ($s1, $s2, $s3) or ($s1 and $s4)
}

Sigma Rule

title: CVE-2024-5928 - VIPRE PMAgent Symlink Abuse
id: 8a3f7c2e-1d5b-4a9c-8e6f-7b2d3c1a5e8f
status: experimental
description: Detects creation of symbolic links in VIPRE directories by low-privileged users
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-5928
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\cmd.exe'
        CommandLine|contains: 'mklink'
        CommandLine|contains: 'VIPRE'
    condition: selection
falsepositives:
    - Administrative maintenance tasks
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-5928 - VIPRE PMAgent Potential Exploitation"; flow:to_server; content:"VIPRE"; nocase; content:"PMAgent"; nocase; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict Permissions: Ensure that only SYSTEM and Administrators have write access to C:\ProgramData\VIPRE\Temp and similar directories.
2. Disable PMAgent: If not required, disable the Patch Management Agent service to eliminate the attack vector.
3. Monitor for Symlink Creation: Deploy detection rules (YARA, Sigma) to alert on symlink creation in VIPRE directories.
4. Apply Least Privilege: Limit user accounts to the minimum necessary privileges to reduce the attack surface.

Long-Term Fix:

• Await an official patch from VIPRE. Contact VIPRE support for updates.
• Consider replacing VIPRE Advanced Security with an alternative endpoint protection solution if a patch is not released in a timely manner.

Workaround:

• Use Windows Defender Application Control (WDAC) or AppLocker to block mklink execution for non-administrative users.
• Enable Sysmon and monitor Event ID 1 (Process Creation) for suspicious mklink commands.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert