CVE-2019-25343: NextVPN Privilege Escalation Vulnerability

CVE-2019-25343 Overview

CVE-2019-25343 is an insecure file permissions vulnerability affecting NextVPN version 4.10. The vulnerability allows local users to modify executable files due to improperly configured access rights. Attackers with local access can exploit this flaw to replace system executables with malicious files, potentially gaining SYSTEM or Administrator privileges through unauthorized file modification.

This vulnerability is classified under CWE-732 (Incorrect Permission Assignment for Critical Resource), which describes scenarios where software does not properly restrict access to critical resources, enabling unauthorized actors to read or modify sensitive data.

Critical Impact

Local privilege escalation to SYSTEM or Administrator level through replacement of executable files with malicious payloads.

Affected Products

• NextVPN version 4.10

Discovery Timeline

• 2026-02-12 - CVE-2019-25343 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2019-25343

Vulnerability Analysis

The vulnerability exists due to insecure file permissions configured on NextVPN 4.10's installation directory and executable files. When NextVPN is installed, the file system permissions are set in a manner that grants overly permissive access rights to local users. This configuration flaw allows any authenticated local user to modify, replace, or overwrite critical executable files within the NextVPN installation path.

The attack requires local access to the system where NextVPN is installed. Once an attacker has gained access as a low-privileged user, they can leverage the misconfigured permissions to replace legitimate NextVPN executables with malicious binaries. When the VPN service or application is subsequently executed (either manually by an administrator or automatically as a scheduled service), the malicious code runs with elevated privileges—typically SYSTEM or Administrator level, depending on how the service is configured.

Root Cause

The root cause of this vulnerability is improper access control list (ACL) configuration during the NextVPN installation process. The installer fails to set restrictive permissions on the application directory and its executables, leaving them writable by standard users. Properly secured applications should ensure that executable files and installation directories are only writable by administrators or the SYSTEM account.

Attack Vector

The attack vector is local, requiring the attacker to have authenticated access to the target system. The exploitation follows a classic DLL hijacking or binary replacement pattern:

1. The attacker identifies the NextVPN installation directory with insecure permissions
2. The attacker creates a malicious executable designed to perform privileged operations
3. The attacker replaces the legitimate NextVPN executable with the malicious version
4. When the NextVPN service restarts or an administrator launches the application, the malicious code executes with elevated privileges

Technical details and proof-of-concept information can be found in the Exploit-DB #47831 entry and the VulnCheck Advisory on NextVPN.

Detection Methods for CVE-2019-25343

Indicators of Compromise

• Unexpected modifications to files within the NextVPN installation directory, particularly executables
• Changes to file timestamps, hashes, or digital signatures of NextVPN binaries
• Presence of unauthorized executables or DLLs in the NextVPN installation path
• Unusual process behavior originating from NextVPN executables

Detection Strategies

• Implement file integrity monitoring (FIM) on the NextVPN installation directory to detect unauthorized modifications
• Monitor Windows Security Event logs for file modification events (Event ID 4663) targeting the NextVPN directory
• Use endpoint detection and response (EDR) solutions to identify anomalous process creation from VPN-related directories
• Regularly audit file system permissions on installed applications to identify overly permissive configurations

Monitoring Recommendations

• Configure SentinelOne agents to monitor and alert on file modifications within VPN application directories
• Enable process behavior monitoring to detect privilege escalation attempts following executable replacement
• Implement baseline integrity checks for critical application executables and alert on deviations
• Monitor for unusual parent-child process relationships involving VPN executables

How to Mitigate CVE-2019-25343

Immediate Actions Required

• Verify file permissions on the NextVPN installation directory and restrict write access to administrators only
• Audit all systems running NextVPN 4.10 for evidence of file modification or compromise
• Consider temporarily disabling or uninstalling NextVPN until proper permissions can be applied
• Implement application whitelisting to prevent execution of unauthorized binaries from the NextVPN directory

Patch Information

Consult the NextVPN vendor for updated versions that address the insecure file permissions issue. Review the VulnCheck Advisory on NextVPN for the latest remediation guidance. If no patch is available, applying manual permission fixes or migrating to an alternative VPN solution may be necessary.

Workarounds

• Manually modify ACLs on the NextVPN installation directory to remove write permissions for standard users
• Use Windows Software Restriction Policies or AppLocker to prevent unauthorized executable modifications
• Run NextVPN under a dedicated service account with minimal privileges
• Deploy endpoint protection solutions capable of detecting and blocking privilege escalation attempts

# PowerShell example to restrict permissions on NextVPN directory
$vpnPath = "C:\Program Files\NextVPN"
$acl = Get-Acl $vpnPath
$acl.SetAccessRuleProtection($true, $false)
$adminRule = New-Object System.Security.AccessControl.FileSystemAccessRule("Administrators","FullControl","ContainerInherit,ObjectInherit","None","Allow")
$systemRule = New-Object System.Security.AccessControl.FileSystemAccessRule("SYSTEM","FullControl","ContainerInherit,ObjectInherit","None","Allow")
$usersRule = New-Object System.Security.AccessControl.FileSystemAccessRule("Users","ReadAndExecute","ContainerInherit,ObjectInherit","None","Allow")
$acl.AddAccessRule($adminRule)
$acl.AddAccessRule($systemRule)
$acl.AddAccessRule($usersRule)
Set-Acl $vpnPath $acl