CVE-2007-1452 in PHP
Summary
by MITRE
The FDF support (ext/fdf) in PHP 5.2.0 and earlier does not implement the input filtering hooks for ext/filter, which allows remote attackers to bypass web site filters via an application/vnd.fdf formatted POST.
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Analysis
by VulDB Data Team • 02/18/2025
The vulnerability described in CVE-2007-1452 represents a critical security flaw in PHP's handling of Forms Data Format files within its FDF extension. This issue affects PHP versions 5.2.0 and earlier, where the FDF support lacks proper input filtering mechanisms that are typically implemented through the ext/filter extension. The fundamental problem lies in the absence of input validation hooks that would normally intercept and process data before it reaches the application layer. When a web application processes FDF-formatted POST data, the missing filtering implementation creates a pathway for attackers to circumvent security measures that should normally validate or sanitize input. This vulnerability directly impacts the principle of least privilege and input validation, which are core tenets of secure software development practices.
The technical flaw manifests when PHP applications that utilize FDF functionality fail to apply the standard input filtering mechanisms that are available through the ext/filter extension. The FDF format is commonly used for exchanging form data between PDF documents and web applications, making it a legitimate data exchange mechanism. However, the absence of proper filtering hooks means that malicious FDF data can bypass the normal sanitization processes that would typically occur when processing form submissions. Attackers can craft specially formatted FDF content that contains malicious payloads, which then gets processed without the usual security checks that would normally occur during standard form data processing. This creates a vector for bypassing web application firewalls, intrusion detection systems, and other security controls that rely on proper input validation.
The operational impact of this vulnerability is significant for web applications that process FDF data, particularly those that handle sensitive information or implement security controls. Remote attackers can exploit this weakness to inject malicious content that would normally be filtered out, potentially leading to cross-site scripting attacks, data injection, or other forms of code execution. The vulnerability undermines the security model of applications that depend on PHP's input filtering capabilities, as the FDF extension operates outside the normal filtering pipeline. This issue affects the integrity of data processing workflows and can compromise the security posture of entire web applications. The vulnerability is particularly dangerous because it operates silently, allowing attackers to bypass security controls without generating detectable anomalies in the application's behavior.
Mitigation strategies for CVE-2007-1452 require immediate action to upgrade affected PHP installations to versions that properly implement input filtering hooks for FDF processing. Organizations should disable FDF support in PHP when it is not strictly required for application functionality, as this eliminates the attack surface entirely. Security administrators should implement additional monitoring for FDF data processing within web applications and establish network-level controls to detect and block suspicious FDF content. The vulnerability aligns with CWE-20, which describes improper input validation, and represents a specific case of how missing security controls in specialized extensions can create exploitable gaps in application security. From an ATT&CK perspective, this vulnerability maps to techniques involving input validation bypass and can be leveraged as part of initial access or privilege escalation campaigns. Organizations should also consider implementing web application firewalls that can detect and block malicious FDF content, while maintaining comprehensive logging of all FDF processing activities for forensic analysis purposes.