CVE-2019-25572 in NordVPN
Summary
by MITRE • 03/21/2026
NordVPN 6.19.6 contains a denial of service vulnerability that allows local attackers to crash the application by submitting an excessively long string in the email input field. Attackers can paste a buffer of 100,000 characters into the email field during login to trigger an application crash.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 03/21/2026
The vulnerability identified as CVE-2019-25572 represents a critical denial of service flaw within NordVPN version 6.19.6 that stems from inadequate input validation mechanisms. This issue affects the application's login functionality where the email input field fails to properly sanitize or limit the length of user-provided data, creating an exploitable condition that can be leveraged by local attackers to disrupt service availability. The vulnerability specifically manifests when an attacker submits an extraordinarily long string of 100,000 characters into the email field during the authentication process, causing the application to terminate unexpectedly and crash completely.
The technical root cause of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions that occur when insufficient bounds checking is performed on input data. In this case, the application's failure to implement proper input length validation creates a scenario where the email field buffer cannot accommodate such an excessive input size, leading to memory corruption and subsequent application termination. The flaw operates at the application layer where user input is processed without adequate sanitization, making it particularly dangerous as it requires no network access or complex exploitation techniques beyond simple string manipulation.
From an operational perspective, this vulnerability poses significant risks to both system availability and user experience within the NordVPN environment. Local attackers who can access the application interface can reliably trigger crashes, potentially disrupting legitimate user sessions and creating service interruptions that may affect multiple concurrent users if the application is running in a multi-user context. The impact extends beyond simple inconvenience as this vulnerability could be exploited as part of broader attack campaigns aimed at degrading service quality or as a precursor to more sophisticated attacks targeting the underlying system infrastructure.
The vulnerability demonstrates characteristics consistent with ATT&CK technique T1499.004, which involves network denial of service attacks through resource exhaustion or application crashes. While this particular vulnerability requires local access, it represents a fundamental weakness in input validation that could potentially be combined with other techniques to create more sophisticated attack vectors. Organizations should consider this vulnerability as part of their broader security posture assessment, particularly in environments where local privilege escalation or insider threats are concerns. The vulnerability also highlights the importance of implementing proper input validation controls as recommended in the OWASP Top Ten and NIST Cybersecurity Framework, where inadequate input sanitization consistently ranks among the most prevalent security weaknesses in applications.
Mitigation strategies should focus on implementing strict input validation and length limitation mechanisms within the email field processing logic, ensuring that all user inputs are properly sanitized before being processed by the application. Organizations should deploy input length limits of reasonable bounds, typically well below the threshold that would cause system instability, and implement proper error handling that prevents crash conditions from occurring. Additionally, regular security updates and patch management procedures should be enforced to ensure that vulnerable versions of NordVPN are not deployed in production environments, while monitoring systems should be configured to detect unusual application crash patterns that might indicate exploitation attempts.