CVE-2019-5421 in Devise
Summary
by MITRE
Plataformatec Devise version 4.5.0 and earlier, using the lockable module contains a CWE-367 vulnerability in The `Devise::Models::Lockable` class, more specifically at the `#increment_failed_attempts` method. File location: lib/devise/models/lockable.rb that can result in Multiple concurrent requests can prevent an attacker from being blocked on brute force attacks. This attack appear to be exploitable via Network connectivity - brute force attacks. This vulnerability appears to have been fixed in 4.6.0 and later.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 08/22/2023
The vulnerability identified as CVE-2019-5421 represents a critical security flaw within the Plataformatec Devise authentication framework version 4.5.0 and earlier. This issue specifically affects applications utilizing the lockable module, which is designed to prevent brute force attacks by temporarily blocking users after multiple failed authentication attempts. The vulnerability stems from a time-of-check to time-of-use (TOCTOU) race condition in the `Devise::Models::Lockable` class, particularly within the `#increment_failed_attempts` method. The flaw allows concurrent requests to interfere with the account lockout mechanism, effectively undermining the security controls intended to protect against automated attack vectors. This vulnerability falls under CWE-367, which specifically addresses time-of-check to time-of-use flaws, making it a particularly dangerous issue for authentication systems.
The technical implementation of this vulnerability occurs when multiple concurrent requests attempt to access a locked account simultaneously. The `increment_failed_attempts` method in lib/devise/models/lockable.rb does not properly synchronize concurrent access to the account lockout state, allowing attackers to bypass the intended rate limiting mechanisms. When an attacker sends multiple simultaneous authentication requests against a locked account, the system may not correctly increment the failed attempt counter or may incorrectly allow access due to race conditions in the database transaction handling. This creates a scenario where an attacker can make multiple authentication attempts before the system properly locks the account, effectively nullifying the brute force protection mechanisms. The vulnerability is particularly concerning because it requires only network connectivity to exploit, making it accessible to anyone with network access to the vulnerable application.
The operational impact of CVE-2019-5421 extends beyond simple bypass of account lockout mechanisms, creating significant risks for organizations relying on Devise for user authentication. Attackers can effectively perform brute force attacks against locked accounts without being properly blocked, potentially leading to account compromise through credential stuffing or password spraying attacks. The vulnerability undermines the fundamental security principle of rate limiting and account lockout functionality, which are essential controls in preventing automated attacks. Organizations using affected versions of Devise may experience increased risk of unauthorized account access, particularly in environments where attackers have the capability to generate multiple concurrent requests. This vulnerability directly impacts the security posture of applications using Devise, potentially exposing sensitive user data and system resources to unauthorized access. The attack surface is particularly broad since Devise is widely used in ruby on rails applications, making this vulnerability prevalent across numerous web applications.
The remediation for CVE-2019-5421 requires upgrading to Devise version 4.6.0 or later, where the race condition in the lockable module has been properly addressed through improved synchronization mechanisms. Organizations should immediately assess their application environments to identify all instances running vulnerable versions of Devise and implement the necessary upgrade process. Security teams should also consider implementing additional monitoring for failed authentication attempts and account lockout events to detect potential exploitation of this vulnerability. The fix implemented in version 4.6.0 typically involves proper database transaction handling and synchronization to ensure that concurrent requests do not interfere with the account lockout state. Organizations should also review their authentication policies and consider implementing additional security controls such as multi-factor authentication, IP-based restrictions, and more robust rate limiting mechanisms as defense-in-depth measures. This vulnerability aligns with ATT&CK technique T1110.003 for Brute Force: Password Guessing and demonstrates the importance of proper concurrency control in authentication systems. The vulnerability serves as a reminder of the critical need for secure coding practices in authentication frameworks and the potential consequences of race conditions in security-sensitive code paths.