CVE-2016-5772 in macOS
Summary
by MITRE
Double free vulnerability in the php_wddx_process_data function in wddx.c in the WDDX extension in PHP before 5.5.37, 5.6.x before 5.6.23, and 7.x before 7.0.8 allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via crafted XML data that is mishandled in a wddx_deserialize call.
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Analysis
by VulDB Data Team • 09/20/2022
The CVE-2016-5772 vulnerability represents a critical double free memory corruption issue within PHP's WDDX (Web Distributed Data Exchange) extension, which has significant implications for web application security. This vulnerability specifically affects the php_wddx_process_data function in the wddx.c source file, where improper memory management leads to a scenario where the same memory block is freed twice during the processing of crafted XML data. The WDDX extension is designed to serialize and deserialize data between different platforms and languages, making it a commonly used component in web applications that require data interchange capabilities. The vulnerability exists across multiple PHP versions including PHP 5.5.x before 5.5.37, PHP 5.6.x before 5.6.23, and PHP 7.x before 7.0.8, indicating a widespread impact across the PHP ecosystem.
The technical flaw stems from inadequate input validation and memory management within the wddx_deserialize function, which processes XML data containing WDDX structures. When maliciously crafted XML data is passed to this function, the parser fails to properly track memory allocations and deallocations, leading to a double free condition where the same memory pointer is released twice. This type of vulnerability falls under CWE-415, which specifically addresses double free conditions in memory management. The improper handling occurs during the deserialization process when the function encounters malformed or specially constructed WDDX data that triggers unexpected memory cleanup operations, causing the memory allocator to become corrupted and potentially leading to arbitrary code execution or application crash.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a potential path for remote code execution in vulnerable environments. Attackers can leverage this vulnerability by sending crafted XML data to applications that utilize the wddx_deserialize function, potentially causing application crashes that lead to denial of service or more critically, allowing for arbitrary code execution. The vulnerability is particularly dangerous because WDDX deserialization is often used in web applications for data interchange, making it a common attack surface. According to ATT&CK framework, this vulnerability maps to T1203 - Exploitation for Client Execution and T1499 - Endpoint Denial of Service, as it can be exploited to compromise system availability and potentially gain unauthorized code execution. The attack vector requires only a single HTTP request containing maliciously crafted XML data, making it easily exploitable in web environments where PHP applications process external input.
Mitigation strategies for CVE-2016-5772 focus primarily on immediate version upgrades to patched PHP releases, with administrators urged to update to PHP 5.5.37, 5.6.23, or 7.0.8 respectively. Additionally, input validation and sanitization measures should be implemented to filter out potentially malicious XML data before it reaches the WDDX deserialization functions. Organizations should consider disabling the WDDX extension entirely if it is not actively required for their applications, as this eliminates the attack surface entirely. Network-level protections such as web application firewalls can help detect and block malicious XML payloads, though these solutions are not foolproof against sophisticated attacks. The vulnerability highlights the importance of proper memory management practices in interpreted languages and underscores the need for comprehensive security testing of extension modules that handle external data input. Security monitoring should include detection of unusual application crashes or memory allocation patterns that might indicate exploitation attempts. Regular security audits of PHP applications should verify proper usage of serialization functions and ensure that all input data is properly validated before processing by potentially vulnerable extension functions.