CVE-2015-2309 In Symfony: Mitigation Guide

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Understanding the High-Severity Vulnerability: CVE-2015-2309

This article delves into the specifics of CVE-2015-2309, a high-severity vulnerability detected in symfony/http-foundation-v2.6.4. We'll break down the vulnerability, its potential impact, and, most importantly, how to mitigate it effectively. This issue arises from a flaw within the Symfony HttpFoundation Component, potentially exposing your application to man-in-the-middle attacks. Ensuring you understand and address this vulnerability is critical for maintaining the security and integrity of your Symfony-based applications.

Detailed Look at the Vulnerable Library

It's important to identify this specific version of the symfony/http-foundation library within your project's dependencies to accurately assess your exposure to this vulnerability. Understanding the component at risk allows you to prioritize your remediation efforts.

Deep Dive into CVE-2015-2309 Vulnerability Details

CVE-2015-2309 is a critical security flaw affecting Symfony versions prior to 2.3.27, 2.5.11, and 2.6.6. The vulnerability stems from how the Symfony\Component\HttpFoundation\Request class handles HTTP header values from potentially untrusted clients. Specifically, the class incorrectly assumes that the remote address is always trustworthy if at least one trusted proxy is involved in the request. This flawed assumption opens the door for man-in-the-middle (MITM) attacks between the last trusted proxy and the web server, allowing malicious actors to intercept and manipulate communications.

  • Vulnerability: Man-in-the-Middle (MITM) Attack
  • Affected Versions: Symfony before 2.3.27, 2.5.11, and 2.6.6
  • Root Cause: Improper handling of HTTP header values from untrusted clients.
  • Attack Vector: Exploitation of trust assumptions in proxy configurations.
  • Publish Date: October 02, 2025 09:59 AM
  • URL: CVE-2015-2309
  • Score: 7.5 (High Severity)

Understanding the Impact of a MITM Attack

Man-in-the-middle attacks are particularly dangerous because they allow attackers to eavesdrop on and potentially alter communications between two parties without either party knowing. In the context of CVE-2015-2309, a successful MITM attack could allow an attacker to:

  • Intercept sensitive data: This includes user credentials, session tokens, and other confidential information transmitted between the client and the server.
  • Modify requests and responses: Attackers could alter the content of requests, potentially injecting malicious code or manipulating application logic.
  • Impersonate users: By capturing user credentials, attackers could gain unauthorized access to user accounts and perform actions on their behalf.
  • Compromise the web server: In some cases, attackers could use the MITM attack as a stepping stone to gain further access to the web server itself.

The high severity score of 7.5 underscores the potential impact of this vulnerability. It is essential to address this issue promptly to protect your application and its users from these serious threats.

Remediation: How to Fix CVE-2015-2309

The recommended solution for CVE-2015-2309 is to upgrade your Symfony installation to a patched version. Specifically, you should upgrade to one of the following versions:

  • v2.3.27 or later
  • v2.5.11 or later
  • v2.6.6 or later

Steps to Upgrade Your Symfony Version

  1. Check Your Current Version: Determine the version of Symfony you are currently using. You can typically find this information in your composer.json file or by running the php bin/console --version command.

  2. Update Your composer.json File: Modify your composer.json file to specify the desired patched version of the symfony/http-foundation component. For example:

    "require": {
    "symfony/http-foundation": "^2.6.6"
}

    Note: The ^ symbol indicates that Composer should install the latest version within the 2.6.x branch that is compatible with your other dependencies. Adjust the version constraint as needed based on your project's requirements.

  3. Run composer update: Execute the composer update symfony/http-foundation command in your terminal. This command will instruct Composer to download and install the specified version of the symfony/http-foundation component and update your project's autoloader.

  4. Clear Your Cache: After upgrading, it's essential to clear your application's cache to ensure that the changes are applied correctly. You can typically do this by running the php bin/console cache:clear command.

  5. Test Your Application: Thoroughly test your application after upgrading to ensure that everything is working as expected. Pay particular attention to areas of your application that handle user input or interact with external services.

Additional Security Measures

In addition to upgrading your Symfony version, consider implementing the following security measures to further protect your application:

  • Implement a Web Application Firewall (WAF): A WAF can help protect your application from a wide range of attacks, including MITM attacks. WAFs work by inspecting HTTP traffic and blocking malicious requests before they reach your application.
  • Use HTTPS: Ensure that your application is using HTTPS to encrypt all communication between the client and the server. This will help prevent attackers from eavesdropping on sensitive data.
  • Regularly Update Your Dependencies: Keep your Symfony installation and all of its dependencies up to date with the latest security patches. This will help protect your application from known vulnerabilities.

Conclusion

Addressing CVE-2015-2309 is crucial for maintaining the security of your Symfony applications. By upgrading to a patched version and implementing additional security measures, you can significantly reduce your risk of being compromised by MITM attacks. Stay vigilant and proactive in your security efforts to protect your application and its users.

For more information on web application security, you can visit the OWASP (Open Web Application Security Project) website: https://owasp.org/. This is a trusted resource for developers and security professionals.