CVE-2007-0908 in PHP
Summary
by MITRE
The WDDX deserializer in the wddx extension in PHP 5 before 5.2.1 and PHP 4 before 4.4.5 does not properly initialize the key_length variable for a numerical key, which allows context-dependent attackers to read stack memory via a wddxPacket element that contains a variable with a string name before a numerical variable.
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Analysis
by VulDB Data Team • 01/30/2025
The vulnerability identified as CVE-2007-0908 represents a critical memory disclosure issue within PHP's WDDX deserialization functionality. This flaw exists in PHP versions prior to 5.2.1 for PHP 5 and 4.4.5 for PHP 4, specifically affecting the wddx extension that handles Web Distributed Data eXchange protocol processing. The vulnerability stems from improper initialization of the key_length variable during the deserialization of WDDX packet elements, creating a scenario where attackers can exploit the uninitialized memory state to extract sensitive data from the application's stack memory.
The technical exploitation of this vulnerability relies on crafting malicious WDDX packet elements that contain variables with mixed naming conventions. When the WDDX deserializer processes a wddxPacket element containing a variable with a string name followed by a numerical variable, the improper initialization of key_length allows attackers to read adjacent memory locations that may contain sensitive information such as stack contents, previously allocated memory segments, or other application data. This memory disclosure occurs because the numerical key's length variable is not properly set before being used in memory operations, leading to undefined behavior that can expose confidential data.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with potential access to sensitive application data that could include session information, database connection details, or other critical system variables. The context-dependent nature of this vulnerability means that exploitation requires specific conditions where the attacker can control the WDDX input and where the application processes WDDX packets containing the targeted variable ordering. This makes the vulnerability particularly dangerous in web applications that accept user input through WDDX format processing, as it could lead to complete system compromise if combined with other exploitation techniques.
Security practitioners should recognize this vulnerability as a classic example of improper initialization leading to memory corruption issues, which aligns with CWE-457: Use of Uninitialized Variable. The vulnerability also demonstrates characteristics consistent with ATT&CK technique T1059.007: Command and Scripting Interpreter: Python, where attackers may use such memory disclosure capabilities to gather intelligence before launching more sophisticated attacks. Organizations should prioritize immediate patching of affected PHP versions, implement proper input validation for WDDX data, and consider disabling the WDDX extension if it is not actively required for application functionality. Additionally, monitoring for unusual WDDX processing patterns and implementing robust application-level security controls can help mitigate the risk associated with this memory disclosure vulnerability.