CVE-2016-7413 in macOS
Summary
by MITRE
Use-after-free vulnerability in the wddx_stack_destroy function in ext/wddx/wddx.c in PHP before 5.6.26 and 7.x before 7.0.11 allows remote attackers to cause a denial of service or possibly have unspecified other impact via a wddxPacket XML document that lacks an end-tag for a recordset field element, leading to mishandling in a wddx_deserialize call.
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Analysis
by VulDB Data Team • 10/07/2022
The CVE-2016-7413 vulnerability represents a critical use-after-free flaw in PHP's XML handling mechanism that affects versions prior to 5.6.26 and 7.0.11. This vulnerability exists within the wddx_stack_destroy function located in ext/wddx/wddx.c, which is responsible for managing the destruction of WDDX (Web Distributed Data Exchange) stack elements during XML processing. The flaw specifically manifests when processing malformed WDDX XML documents that lack proper end-tags for recordset field elements, creating a scenario where memory management becomes compromised during deserialization operations. The vulnerability demonstrates the classic characteristics of a use-after-free condition where previously freed memory locations are accessed, potentially leading to unpredictable behavior and system instability.
The technical exploitation of this vulnerability occurs through the manipulation of WDDX XML packet structures that are processed by PHP's wddx_deserialize function. When a malformed XML document is presented to the PHP parser with missing end-tags for recordset field elements, the internal stack management mechanism fails to properly handle the memory cleanup process. This improper handling creates a situation where memory allocated for stack elements is freed but subsequently accessed during the destruction phase, leading to potential memory corruption. The vulnerability is particularly dangerous because it can be triggered through remote XML processing operations, making it exploitable over network connections without requiring local system access. The flaw operates at the intersection of memory management and XML parsing, where the parser's failure to validate proper XML structure leads to improper memory deallocation sequences.
The operational impact of CVE-2016-7413 extends beyond simple denial of service to potentially enable more severe consequences including arbitrary code execution and system compromise. When exploited successfully, this vulnerability can cause PHP processes to crash, leading to denial of service conditions that disrupt web application availability. However, the use-after-free nature suggests that attackers might potentially leverage this condition to execute arbitrary code by carefully crafting malicious XML payloads that manipulate memory layout and execution flow. The vulnerability affects PHP's WDDX extension, which is commonly used for data serialization and communication between web applications, making it particularly dangerous in environments where XML data processing is prevalent. Security researchers have classified this issue under CWE-416, which specifically addresses use-after-free vulnerabilities, and the attack surface aligns with ATT&CK technique T1203, focusing on exploitation of memory corruption vulnerabilities.
Organizations affected by this vulnerability should prioritize immediate patching of their PHP installations to versions 5.6.26 and 7.0.11 or later, as these releases contain the necessary fixes for the memory management issues in the wddx_stack_destroy function. System administrators should implement network-level filtering to restrict access to XML processing endpoints and monitor for unusual patterns in XML data submissions that might indicate exploitation attempts. Additional mitigations include implementing proper input validation for all XML data received by PHP applications, disabling unnecessary WDDX functionality when not required, and deploying intrusion detection systems to monitor for malformed XML payloads. The vulnerability highlights the importance of proper memory management in XML parsing libraries and serves as a reminder of the critical need for thorough input validation and secure coding practices in web application development. Security teams should also consider implementing application firewalls and web application security monitoring solutions to detect and prevent exploitation attempts targeting this specific vulnerability pattern.