In this post, we will discuss a significant security vulnerability in the Symphony PHP framework, specifically related to its authentication system. CVE-2024-51996 is a critical authentication bypass issue that affects Symphony's process module, which is responsible for executing commands in sub-processes. This vulnerability lies in the consumption of a persisted remember-me cookie, where Symphony fails to verify if the username persisted in the database matches the username attached to the cookie. Consequently, it allows attackers to bypass the authentication system and gain unauthorized access to users' accounts.

We will go through the details of this vulnerability, share code snippets highlighting the vulnerable code, and provide links to original references. Finally, we will discuss the patches released by the Symphony team in versions 5.4.47, 6.4.15, and 7.1.8 that address this security issue.

Vulnerability Details

CVE-2024-51996 stems from the lack of proper validation when Symfony consumes a remember-me cookie. In many web applications, remember-me cookies are used to enable users' authentication sessions to persist across multiple visits. However, during the consumption process, Symfony fails to ensure that the username persisted in the database matches the one attached to the cookie. This oversight could allow an attacker to bypass the system's authentication and potentially access other users' accounts.

To better understand the issue, let's look at a simplified code snippet that illustrates the vulnerable code:

class RememberMeAuthentication {
    public function authenticate(Request $request) {
        // Read the remember-me cookie from the request
        $cookie = $request->get('remember_me');

        // Extract the username from the cookie
        $username = $this->extractUsernameFromCookie($cookie);

        // Lookup the user in the database
        $user = $this->userRepository->findUserByUsername($username);

        // Log the user in
        $this->login($user);
    }
}

As shown in the snippet above, the authenticate function processes the remember-me cookie, extracting the username from it, and looks up that user in the database by username. Afterward, the $this->login($user) function logs in the user, completing the authentication process. However, there is no check to validate whether the username persisted in the database matches the one associated with the cookie, allowing attackers to potentially exploit this behavior for authentication bypass.

For full technical details on the vulnerability, please refer to the official security advisories

1. Symfony Security Advisory
2. NIST National Vulnerability Database

Patch and Mitigation

To address this vulnerability, the Symfony team introduced patches in versions 5.4.47, 6.4.15, and 7.1.8. These updates include additional checks and validation to ensure that the username persisted in the database matches the one attached to the remember-me cookie during the authentication process. Applying these patches is crucial for organizations using vulnerable versions of Symfony to safeguard their systems against potential exploitation of this security issue.

Here is an example of how the vulnerable code from the snippet above has been patched to validate the username properly:

class RememberMeAuthentication {
    public function authenticate(Request $request) {
        // Read the remember-me cookie from the request
        $cookie = $request->get('remember_me');

        // Extract the username from the cookie
        $username = $this->extractUsernameFromCookie($cookie);

        // Lookup the user in the database
        $user = $this->userRepository->findUserByUsername($username);

        // Verify if the username in the cookie matches the one in the database
        if ($username !== $user->getUsername()) {
            throw new AuthenticationException("Username mismatch detected.");
        }

        // Log the user in
        $this->login($user);
    }
}

By adding the check for $username !== $user->getUsername() and throwing an AuthenticationException if there's a mismatch, Symfony effectively patches the security vulnerability and prevents authentication bypass attempts.

Conclusion

CVE-2024-51996 is a critical vulnerability affecting the Symfony PHP framework, allowing attackers to bypass authentication by exploiting the lack of proper validation during the consumption of a remember-me cookie. To protect your applications and users, it is crucial to apply the patches provided in versions 5.4.47, 6.4.15, and 7.1.8 of Symfony, which introduce the necessary checks and validation to secure the authentication process.

This analysis serves as a reminder for the importance of regular security assessments, patch management, and rigorous validation procedures in web application development, as even widely-used frameworks such as Symfony can contain vulnerabilities that put users' sensitive information at risk.

Timeline

Published on: 11/13/2024 17:15:11 UTC
Last modified on: 11/15/2024 14:00:09 UTC