CVE-2016-9935 in macOS
Summary
by MITRE
The php_wddx_push_element function in ext/wddx/wddx.c in PHP before 5.6.29 and 7.x before 7.0.14 allows remote attackers to cause a denial of service (out-of-bounds read and memory corruption) or possibly have unspecified other impact via an empty boolean element in a wddxPacket XML document.
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Analysis
by VulDB Data Team • 11/15/2022
The vulnerability identified as CVE-2016-9935 represents a critical security flaw within the PHP web scripting language that affects versions prior to 5.6.29 and 7.0.14. This issue resides within the php_wddx_push_element function located in the ext/wddx/wddx.c source file, which handles the processing of WDDX (Web Distributed Data Exchange) packet XML documents. The vulnerability specifically manifests when processing empty boolean elements within WDDX packets, creating a scenario where remote attackers can exploit this weakness to execute malicious code or disrupt system operations.
The technical nature of this vulnerability involves an out-of-bounds read condition combined with memory corruption capabilities that can be leveraged by attackers to cause denial of service or potentially achieve more severe impacts. When PHP processes a WDDX packet containing an empty boolean element, the php_wddx_push_element function fails to properly validate the element structure, leading to improper memory access patterns. This flaw falls under the CWE-125 vulnerability category, which describes out-of-bounds read conditions that can result in information disclosure, system crashes, or arbitrary code execution. The memory corruption aspect of this vulnerability can be particularly dangerous as it may allow attackers to manipulate memory contents and potentially execute malicious instructions.
The operational impact of CVE-2016-9935 extends beyond simple denial of service scenarios, as the vulnerability can be exploited to compromise entire web applications that utilize PHP for processing WDDX data. Attackers can craft malicious WDDX packet XML documents containing empty boolean elements that, when processed by vulnerable PHP installations, trigger the memory corruption and out-of-bounds read conditions. This vulnerability is particularly concerning in web environments where PHP applications process user-supplied data through WDDX packet parsing, as it can be exploited through various attack vectors including web forms, API endpoints, or file uploads. The ATT&CK framework categorizes this type of vulnerability under the T1059.007 technique for script-based execution, where adversaries leverage the processing of malformed input data to gain unauthorized access or disrupt services.
The mitigation strategy for CVE-2016-9935 requires immediate patching of affected PHP installations to versions 5.6.29 or 7.0.14 and later, which contain the necessary fixes to properly validate WDDX packet elements. Organizations should also implement input validation measures to filter out malformed WDDX packets before they reach the PHP processing layer, particularly when dealing with user-supplied data. Network-based intrusion detection systems can be configured to monitor for patterns associated with WDDX packet exploitation attempts, while application firewalls can help prevent malicious WDDX data from reaching vulnerable PHP applications. Additionally, security teams should conduct thorough vulnerability assessments to identify all systems running affected PHP versions and ensure comprehensive patch management processes are in place to prevent similar vulnerabilities from being exploited in the future.