CVE-2017-16653 in Symfony
Summary
by MITRE
An issue was discovered in Symfony before 2.7.38, 2.8.31, 3.2.14, 3.3.13, 3.4-BETA5, and 4.0-BETA5. The current implementation of CSRF protection in Symfony (Version >=2) does not use different tokens for HTTP and HTTPS; therefore the token is subject to MITM attacks on HTTP and can then be used in an HTTPS context to do CSRF attacks.
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Analysis
by VulDB Data Team • 05/01/2023
The vulnerability described in CVE-2017-16653 represents a critical weakness in Symfony's Cross-Site Request Forgery protection mechanism that has significant implications for web application security. This flaw affects multiple versions of the Symfony framework including the 2.7, 2.8, 3.2, 3.3, and 4.0 release lines, making it a widespread concern across the Symfony ecosystem. The issue stems from the framework's implementation of CSRF tokens that fail to differentiate between secure and non-secure HTTP contexts, creating a fundamental security gap that adversaries can exploit to bypass intended protection measures.
The technical flaw manifests in the improper handling of CSRF tokens across different transport protocols within the Symfony framework. When a user accesses a Symfony application over HTTP, the CSRF token generated is identical to the one used when accessing the same application over HTTPS. This design decision creates a vulnerability where an attacker can intercept a CSRF token transmitted over an unencrypted HTTP connection through man-in-the-middle attacks. Once obtained, this token can be reused in HTTPS contexts to perform CSRF attacks against authenticated users, effectively bypassing the security mechanisms that should protect against unauthorized actions. The vulnerability directly relates to CWE-352, which describes Cross-Site Request Forgery, and specifically addresses the weakness in token management and session handling that allows for protocol-agnostic token reuse.
The operational impact of this vulnerability extends beyond simple token interception, as it enables sophisticated attack vectors that can compromise user sessions and perform unauthorized actions on behalf of authenticated users. Attackers can leverage this vulnerability to execute CSRF attacks in scenarios where users transition between HTTP and HTTPS contexts, particularly during login processes or when applications contain both secure and non-secure resources. This weakness is particularly dangerous because it allows attackers to perform actions that would normally require a valid session token in a secure HTTPS environment, even when they only possess a token obtained through an HTTP interception. The vulnerability can lead to session hijacking, unauthorized transactions, data modification, and other malicious activities that undermine the integrity and confidentiality of web applications using affected Symfony versions.
Organizations utilizing affected Symfony versions should immediately implement comprehensive mitigation strategies to address this vulnerability. The primary recommendation involves upgrading to patched versions of Symfony that properly differentiate CSRF tokens between HTTP and HTTPS contexts, specifically versions 2.7.38, 2.8.31, 3.2.14, 3.3.13, and 3.4-BETA5 or later. Additionally, security teams should consider implementing additional protective measures such as enforcing strict HTTPS usage throughout the application, implementing HSTS (HTTP Strict Transport Security) headers, and ensuring that all CSRF tokens are generated with proper protocol-specific differentiation. Network-level protections including certificate pinning and monitoring for mixed content can also help mitigate the risk of token interception attacks. The vulnerability also highlights the importance of following security best practices outlined in the OWASP Top Ten and aligns with ATT&CK techniques related to credential access and session management, emphasizing the need for robust session token handling and protocol-specific security controls in web application frameworks.