CVE-2016-3141 in Mac OS X
Summary
by MITRE
Use-after-free vulnerability in wddx.c in the WDDX extension in PHP before 5.5.33 and 5.6.x before 5.6.19 allows remote attackers to cause a denial of service (memory corruption and application crash) or possibly have unspecified other impact by triggering a wddx_deserialize call on XML data containing a crafted var element.
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Analysis
by VulDB Data Team • 08/19/2022
The CVE-2016-3141 vulnerability represents a critical use-after-free flaw within PHP's WDDX extension, specifically in the wddx.c file that handles XML data serialization and deserialization operations. This vulnerability affects PHP versions prior to 5.5.33 and 5.6.19, creating a significant security risk for web applications that utilize the WDDX extension for data exchange between PHP applications and other systems. The WDDX (Web Distributed Data Exchange) extension provides a way to serialize and deserialize data structures into XML format, making it a common component in web applications that require data interchange between different systems or platforms.
The technical flaw manifests when the wddx_deserialize function processes XML data containing a specially crafted var element that triggers a use-after-free condition in memory management. This occurs because the function does not properly validate or handle the lifecycle of memory allocated for variable elements during the deserialization process. When a maliciously constructed XML payload is processed through wddx_deserialize, the underlying memory management routines fail to properly track the usage of allocated memory blocks, leading to situations where freed memory is accessed or reused incorrectly. This memory corruption vulnerability stems from improper handling of reference counting or object lifecycle management within the PHP extension's internal code structure, creating opportunities for memory corruption that can be exploited remotely.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable more severe consequences including arbitrary code execution or complete application compromise. Remote attackers can leverage this vulnerability by sending crafted XML data to applications that utilize the wddx_deserialize function, causing memory corruption that results in application crashes or system instability. The potential for unspecified other impacts suggests that under certain conditions, this vulnerability could be escalated to allow attackers to execute malicious code within the context of the affected PHP process. This makes the vulnerability particularly dangerous in web server environments where PHP applications are exposed to untrusted input from external sources, as it could provide a foothold for more extensive attacks against the hosting infrastructure.
Mitigation strategies for CVE-2016-3141 primarily focus on immediate patching of affected PHP installations to versions 5.5.33 or 5.6.19 and later, which contain the necessary memory management fixes. Organizations should also implement input validation and sanitization measures to prevent untrusted XML data from reaching the wddx_deserialize function, particularly when processing external inputs. The vulnerability aligns with CWE-416, which describes the use of freed memory condition, and could be categorized under ATT&CK technique T1059.007 for command and scripting interpreter usage in remote code execution scenarios. Additionally, implementing proper security monitoring and intrusion detection systems can help identify exploitation attempts targeting this specific vulnerability, while disabling the WDDX extension entirely in environments where it is not required provides an additional layer of defense against potential exploitation attempts.