CVE-2016-7398 in pecl-http extension
Summary
by MITRE
A type confusion vulnerability in the merge_param() function of php_http_params.c in PHP's pecl-http extension 3.1.0beta2 (PHP 7) and earlier as well as 2.6.0beta2 (PHP 5) and earlier allows attackers to crash PHP and possibly execute arbitrary code via crafted HTTP requests.
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Analysis
by VulDB Data Team • 12/13/2023
The vulnerability CVE-2016-7398 represents a critical type confusion flaw within the php_http_params.c file of PHP's pecl-http extension, affecting versions up to 3.1.0beta2 for PHP 7 and 2.6.0beta2 for PHP 5. This issue arises from improper handling of data types during parameter merging operations, creating a scenario where the application fails to correctly distinguish between different data structures. The vulnerability specifically manifests in the merge_param() function which processes HTTP parameters, making it a prime target for exploitation through maliciously crafted HTTP requests that manipulate parameter structures.
The technical exploitation of this vulnerability stems from a fundamental flaw in type validation and memory management within the HTTP parameter processing pipeline. When the merge_param() function encounters crafted HTTP requests, it fails to properly validate the types of parameters being merged, leading to a situation where memory corruption occurs. This type confusion allows attackers to manipulate the execution flow of the PHP process by overwriting critical memory locations with malicious data. The vulnerability is classified under CWE-476 as a NULL pointer dereference, though the actual exploitation involves more complex memory manipulation techniques that can lead to arbitrary code execution.
The operational impact of CVE-2016-7398 extends beyond simple service disruption to potentially enable full system compromise when exploited successfully. Attackers can leverage this vulnerability to cause PHP processes to crash repeatedly, leading to denial of service conditions, or more critically, execute arbitrary code on the affected system with the privileges of the web server process. This makes the vulnerability particularly dangerous in web server environments where PHP applications handle user input directly. The attack vector through crafted HTTP requests means that any web application using the affected pecl-http extension could become a target, especially those processing external HTTP inputs without proper validation.
Mitigation strategies for CVE-2016-7398 primarily focus on immediate version updates to patched releases of the pecl-http extension, specifically versions that address the type confusion in merge_param() function. System administrators should prioritize updating their PHP environments to versions that include fixes for this vulnerability, while also implementing proper input validation measures to reduce the attack surface. Network-level defenses such as web application firewalls can provide additional protection by filtering suspicious HTTP requests that might attempt to exploit this vulnerability. The ATT&CK framework categorizes this vulnerability under T1203 as Exploitation for Client Execution, emphasizing the need for both server-side patching and network-based monitoring to detect potential exploitation attempts. Organizations should also consider implementing runtime protections and monitoring for abnormal PHP process behavior that might indicate exploitation attempts, given the potential for privilege escalation and persistent access to compromised systems.