CVE-2014-3622 in PHP
Summary
by MITRE
Use-after-free vulnerability in the add_post_var function in the Posthandler component in PHP 5.6.x before 5.6.1 might allow remote attackers to execute arbitrary code by leveraging a third-party filter extension that accesses a certain ksep value.
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Analysis
by VulDB Data Team • 02/21/2022
The CVE-2014-3622 vulnerability represents a critical use-after-free flaw within PHP's Posthandler component that existed in versions prior to 5.6.1. This vulnerability specifically affects the add_post_var function which handles POST data processing in PHP applications. The flaw occurs when third-party filter extensions attempt to access a particular ksep value during post processing, creating a scenario where freed memory locations are accessed after they have been deallocated. This type of vulnerability falls under the CWE-416 category, which specifically addresses use-after-free conditions that can lead to arbitrary code execution. The vulnerability demonstrates how improper memory management in core PHP components can be exploited through seemingly innocent third-party extensions that interact with the internal data structures.
The technical exploitation of this vulnerability requires a remote attacker to leverage a third-party filter extension that accesses the ksep value in a specific manner. When PHP processes POST data through the Posthandler component, the add_post_var function allocates memory for variables and subsequently frees this memory. However, certain filter extensions may retain references to these freed memory locations, particularly when accessing the ksep value. This creates a window where an attacker can manipulate the memory state to cause the freed memory to be reused for malicious purposes. The vulnerability operates at the intersection of memory management and extension architecture, where the interaction between PHP's core processing and external filter modules creates an exploitable condition. According to ATT&CK framework, this represents a privilege escalation technique through memory corruption, specifically targeting the application layer where PHP processes user input.
The operational impact of CVE-2014-3622 is significant as it allows remote code execution on vulnerable systems, potentially enabling full system compromise. Attackers can exploit this vulnerability to execute arbitrary code with the privileges of the web server process, which typically runs with elevated permissions on the hosting environment. This vulnerability affects web applications that process POST data through PHP, making it particularly dangerous for content management systems, web applications, and any PHP-based platforms that accept user input through HTTP POST requests. The exploitation typically requires the presence of a vulnerable third-party filter extension, making the attack surface somewhat more specific but still highly impactful. Organizations running PHP versions between 5.6.0 and 5.6.1 were particularly vulnerable, though the broader implications extend to any system where PHP processes untrusted POST data through potentially compromised extension modules. The vulnerability demonstrates the importance of proper memory management in server-side scripting environments and highlights how third-party components can introduce critical security risks into otherwise secure applications. Mitigation strategies focus on updating to PHP 5.6.1 or later, which includes the necessary memory management fixes, along with careful review and removal of unnecessary filter extensions that may interact with internal PHP structures.