Symfony2 security issue when the trust proxy mode is enabled
An application is vulnerable if it uses the client IP address as returned by the Request::getClientIp() method for sensitive decisions like IP based access control.
To fix this security issue, the following changes have been made to all versions of Symfony2:
A new Request::setTrustedProxies() method has been introduced and should be used intead of Request::trustProxyData() to enable the trust proxy mode. It takes an array of trusted proxy IP addresses as its argument:
// before (probably in your front controller script)
Request::trustProxyData();
// after
Request::setTrustedProxies(array('1.1.1.1'));
// 1.1.1.1 being the IP address of a trusted reverse proxy
The Request::trustProxyData() method has been deprecated (when used, it automatically trusts the latest proxy in the chain -- which is the current remote address):
Request::trustProxyData();
// is equivalent to
Request::setTrustedProxies(array($request->server->get('REMOTE_ADDR')));
We encourage all Symfony2 users to upgrade as soon as possible. It you don't want to upgrade to the latest version yet, you can also apply the following patches:
| Software | From | Fixed in |
|---|---|---|
symfony / http-foundation
|
2.0.0 | 2.0.19 |
|
symfony / http-foundation
|
2.1.0 | 2.1.4 |
|
symfony / symfony
|
2.0.0 | 2.0.19 |
|
symfony / symfony
|
2.1.0 | 2.1.4 |
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/http-foundation/2012-11-29.yaml
- https://github.com/symfony/http-foundation/commit/5cde5229fc71a19cef2a0a933a18e08e43252f34
- https://github.com/symfony/http-foundation/commit/795ac45c188ee2a729db4513e9dfd30b16a0ed35
- https://github.com/symfony/symfony/commit/9ce892cf4395e73b136e9b5cd1fae9e91995c93b
- https://github.com/symfony/symfony/commit/e5536f0fe10421da7ebbe0071343e94d039dfb97
- https://symfony.com/blog/security-release-symfony-2-0-19-and-2-1-4
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A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.
Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.
Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
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