CVE-2016-7129 in PHP
Summary
by MITRE
The php_wddx_process_data function in ext/wddx/wddx.c in PHP before 5.6.25 and 7.x before 7.0.10 allows remote attackers to cause a denial of service (segmentation fault) or possibly have unspecified other impact via an invalid ISO 8601 time value, as demonstrated by a wddx_deserialize call that mishandles a dateTime element in a wddxPacket XML document.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability identified as CVE-2016-7129 represents a critical security flaw in the PHP web application scripting language that affects versions prior to 5.6.25 and 7.0.10. This issue resides within the php_wddx_process_data function located in the ext/wddx/wddx.c source file, which handles the processing of WDDX (Web Distributed Data Exchange) data structures. The vulnerability specifically manifests when PHP processes invalid ISO 8601 time values through the wddx_deserialize function, creating a potential attack vector that can be exploited by remote adversaries. The flaw occurs during the parsing of dateTime elements within wddxPacket XML documents, where improper validation of time format inputs leads to unpredictable behavior in the application's memory management.
The technical exploitation of this vulnerability leverages malformed ISO 8601 time values that cause the WDDX deserialization process to encounter invalid data structures. When PHP attempts to process these malformed time values, the php_wddx_process_data function fails to properly validate the input, leading to memory corruption issues that result in segmentation faults. This memory corruption can potentially be escalated beyond simple denial of service to more severe impacts including arbitrary code execution, depending on the specific system configuration and memory layout. The vulnerability demonstrates characteristics consistent with CWE-125, which describes out-of-bounds read conditions, and CWE-129, which covers invalid input validation issues. The flaw operates at the intersection of XML parsing and data serialization processes, where the WDDX packet structure fails to properly sanitize time format inputs before processing.
From an operational perspective, this vulnerability presents significant risks to PHP-based web applications that utilize WDDX deserialization features, particularly in environments where user input is processed through these functions. Attackers can craft malicious XML packets containing malformed dateTime elements that trigger the segmentation fault when processed by wddx_deserialize, leading to service disruption and potential system instability. The impact extends beyond simple denial of service as the memory corruption could potentially be exploited for more sophisticated attacks, including privilege escalation or code execution within the affected application context. Organizations running vulnerable PHP versions face the risk of complete service outages and potential data compromise, especially when applications process untrusted XML input through WDDX functions. This vulnerability aligns with ATT&CK technique T1203, which covers exploitation for privilege escalation through memory corruption attacks.
The recommended mitigation strategy involves immediate deployment of patched PHP versions, specifically PHP 5.6.25 and PHP 7.0.10 or later, which contain the necessary fixes for the WDDX deserialization validation. System administrators should also implement input validation measures to filter or sanitize XML data before processing, particularly when dealing with user-supplied content. Additionally, organizations should consider disabling WDDX functionality if it is not essential to their applications, as a defensive measure against potential exploitation. Network-level protections such as XML parsing restrictions and input validation firewalls can provide additional layers of defense. The vulnerability highlights the importance of proper input validation and memory management in serialization functions, emphasizing the need for comprehensive security testing of data parsing components within web applications. Organizations should conduct thorough vulnerability assessments to identify all instances where WDDX functions are utilized and ensure complete patching across their entire infrastructure.