CVE-2019-25572: NordVPN DoS Vulnerability via Email Field

CVE-2019-25572 Overview

CVE-2019-25572 is a denial of service vulnerability affecting NordVPN version 6.19.6 for Windows. The vulnerability allows local attackers to crash the application by submitting an excessively long string in the email input field during the login process. Specifically, attackers can paste a buffer of approximately 100,000 characters into the email field, which triggers an application crash due to improper input validation.

Critical Impact

Local attackers can cause a denial of service condition by crashing the NordVPN application, disrupting VPN connectivity and potentially exposing user network traffic.

Affected Products

• NordVPN 6.19.6 for Windows
• Earlier versions of NordVPN 6.x may also be affected

Discovery Timeline

• 2026-03-21 - CVE CVE-2019-25572 published to NVD
• 2026-03-23 - Last updated in NVD database

Technical Details for CVE-2019-25572

Vulnerability Analysis

This vulnerability is classified under CWE-1260 (Improper Handling of Length Parameter Inconsistency), indicating a fundamental flaw in how the NordVPN application handles input data length in the email field. The application fails to properly validate or limit the size of user-supplied input before processing, leading to resource exhaustion or buffer-related issues when an oversized string is submitted.

The attack requires local access to the system where NordVPN is installed. An attacker can exploit this vulnerability without requiring any special privileges or user interaction, making it straightforward to execute once local access is obtained. The impact is limited to availability—there is no evidence of confidentiality or integrity compromise through this vulnerability.

Root Cause

The root cause stems from improper input validation in the NordVPN login form. The email input field does not enforce adequate length restrictions before passing the data to internal processing functions. When an excessively large string (approximately 100,000 characters) is submitted, the application cannot handle the oversized input gracefully, resulting in an application crash.

This type of vulnerability typically occurs when developers assume input will conform to expected parameters without implementing proper bounds checking. The application should enforce maximum input lengths both on the client-side UI and within the underlying processing logic.

Attack Vector

The attack vector for this vulnerability is local, meaning the attacker must have access to a system where NordVPN is installed. The exploitation process involves:

1. Opening the NordVPN application on the target system
2. Navigating to the login screen
3. Pasting a string of approximately 100,000 characters into the email input field
4. Triggering a crash of the NordVPN application

This attack does not require authentication or elevated privileges, and no user interaction beyond having the application installed is necessary. Additional technical details and a proof-of-concept are available in the Exploit-DB #46343 entry.

Detection Methods for CVE-2019-25572

Indicators of Compromise

• NordVPN application crashes or unexpected termination events in Windows Event Logs
• Application crash dump files in the NordVPN installation or Windows crash directories
• Unusual clipboard activity involving extremely large text strings
• Multiple application restart events in a short time frame

Detection Strategies

• Monitor Windows Event Logs for NordVPN application crash events (Event ID 1000, Application Error)
• Implement endpoint detection rules to identify abnormal text input sizes in application fields
• Deploy SentinelOne behavioral AI to detect and alert on application crash patterns
• Configure process monitoring to track NordVPN process termination events

Monitoring Recommendations

• Enable detailed application crash logging on systems running NordVPN
• Implement centralized log collection for endpoint security events
• Create alerts for repeated NordVPN application crashes on the same system
• Monitor for suspicious clipboard operations involving large data transfers

How to Mitigate CVE-2019-25572

Immediate Actions Required

• Update NordVPN to the latest available version from the official NordVPN website
• Restrict local access to systems where NordVPN is installed to authorized users only
• Download the latest NordVPN installer from the official download link
• Review the VulnCheck Advisory for additional guidance

Patch Information

Organizations should update NordVPN to the latest version to ensure this vulnerability is addressed. The latest NordVPN installer can be obtained from the official NordVPN website. Verify the integrity of the downloaded installer before deployment across enterprise environments.

Workarounds

• Limit physical and remote access to workstations running NordVPN to trusted users
• Implement application whitelisting to prevent unauthorized modifications or tampering
• Deploy endpoint protection solutions like SentinelOne to detect and respond to application crashes
• Consider using network-based VPN solutions if endpoint VPN stability is a concern

If immediate patching is not possible, organizations should ensure that only authorized personnel have local access to systems running the vulnerable NordVPN version, as exploitation requires local access to the target machine.