CVE-2018-25368: Nord VPN DOS Vulnerability

CVE-2018-25368 Overview

CVE-2018-25368 is a denial of service vulnerability in NordVPN version 6.14.31. The flaw allows unauthenticated attackers with local access to the login interface to crash the application by submitting an excessively long string into the password field. Pasting a buffer of repeated characters into the password input triggers an application crash during authentication. The underlying weakness is classified as [CWE-789] (Memory Allocation with Excessive Size Value). The vulnerability affects availability of the NordVPN desktop client without exposing credentials or enabling code execution.

Critical Impact

Attackers can repeatedly crash the NordVPN client through oversized password input, disrupting VPN connectivity for affected users.

Affected Products

• NordVPN 6.14.31 desktop client

Discovery Timeline

• 2026-05-25 - CVE-2018-25368 published to NVD
• 2026-05-26 - Last updated in NVD database

Technical Details for CVE-2018-25368

Vulnerability Analysis

The vulnerability resides in the NordVPN 6.14.31 client login workflow. The application fails to validate or constrain the length of input supplied to the password field. When an attacker pastes a long buffer of repeated characters and submits the credentials, the client crashes during authentication processing. The defect is a denial of service condition affecting the client process only. It does not produce confidentiality or integrity loss because no code execution or memory disclosure has been demonstrated. The flaw is referenced in Exploit-DB entry 45304 and the VulnCheck advisory.

Root Cause

The root cause maps to [CWE-789], memory allocation with an excessive size value driven by attacker-controlled input. The client accepts an unbounded password string and attempts to process it without enforcing a maximum length. The resulting allocation or string handling operation triggers a fatal error inside the client process. Input sanitization on the password field is absent, so any repeated-character payload large enough to exceed internal buffer or allocation thresholds causes the crash.

Attack Vector

The attack requires interaction with the NordVPN client login form. An attacker with access to an unlocked workstation, or a user tricked into pasting a malicious string, can trigger the crash. No prior authentication is needed because the input is processed before credential validation completes. Each crash forces the user to relaunch the client and re-establish the VPN tunnel, which can be repeated to sustain denial of service. The vulnerability cannot be triggered from a remote network attacker without access to the local login UI.

The vulnerability manifests when oversized input reaches the password handler. See the VulnCheck advisory for NordVPN and Exploit-DB #45304 for technical reproduction details.

Detection Methods for CVE-2018-25368

Indicators of Compromise

• Repeated unexpected terminations of the NordVPN client process on Windows endpoints running version 6.14.31.
• Windows Application Event Log entries showing crashes of the NordVPN executable with faulting module references during login attempts.
• Loss of VPN tunnel connectivity correlated with user reports of client failures at the login screen.

Detection Strategies

• Monitor endpoint telemetry for abnormal exit codes or crash dumps generated by the NordVPN client binary.
• Correlate process termination events with active user sessions on the login UI to identify attempted exploitation.
• Alert on NordVPN 6.14.31 instances still present in the environment by inventorying installed software versions.

Monitoring Recommendations

• Inventory all endpoints running NordVPN and confirm version numbers through software asset management.
• Forward Windows Error Reporting (WER) crash events for the NordVPN process to a central log platform for review.
• Track user-reported VPN disconnections to surface patterns consistent with repeated client crashes.

How to Mitigate CVE-2018-25368

Immediate Actions Required

• Upgrade NordVPN clients to the current release available from the NordVPN download page, which supersedes 6.14.31.
• Restrict physical and remote access to endpoints where the NordVPN client login UI is exposed to untrusted users.
• Educate users not to paste untrusted content into VPN client credential fields.

Patch Information

NordVPN distributes updated client builds through the official NordVPN download page. Users running 6.14.31 should uninstall the affected version and install the latest supported client. No vendor-specific patch identifier is published in the NVD record for this CVE.

Workarounds

• Lock workstations when unattended to prevent unauthorized interaction with the NordVPN login dialog.
• Use endpoint management policies to enforce a minimum approved NordVPN client version across the fleet.
• Disable shared or kiosk accounts that allow arbitrary users to reach the VPN client login screen.

# Configuration example: query installed NordVPN version on Windows endpoints
powershell -Command "Get-ItemProperty HKLM:\Software\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall\* | Where-Object { $_.DisplayName -like 'NordVPN*' } | Select-Object DisplayName, DisplayVersion"