CVE-2014-9705 in PHP
Summary
by MITRE
Heap-based buffer overflow in the enchant_broker_request_dict function in ext/enchant/enchant.c in PHP before 5.4.38, 5.5.x before 5.5.22, and 5.6.x before 5.6.6 allows remote attackers to execute arbitrary code via vectors that trigger creation of multiple dictionaries.
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Analysis
by VulDB Data Team • 04/16/2022
The vulnerability identified as CVE-2014-9705 represents a critical heap-based buffer overflow flaw within the PHP enchant extension, specifically affecting the enchant_broker_request_dict function in the ext/enchant/enchant.c file. This vulnerability exists in PHP versions prior to 5.4.38, 5.5.x prior to 5.5.22, and 5.6.x prior to 5.6.6, making it a widespread issue across multiple PHP release branches. The flaw manifests when the enchant extension processes requests for dictionary creation, particularly when multiple dictionaries are being created simultaneously, creating a scenario where memory corruption can occur in the heap memory allocation region. The vulnerability is classified under CWE-121 as a heap-based buffer overflow, which represents a fundamental memory safety issue where data written to memory locations beyond the allocated buffer boundaries can overwrite adjacent memory structures. This type of vulnerability is particularly dangerous as it can lead to arbitrary code execution, making it a prime target for exploitation by malicious actors seeking to compromise PHP-based web applications.
The technical exploitation of this vulnerability occurs through carefully crafted inputs that trigger the creation of multiple dictionaries within the enchant extension, which is commonly used for spell checking functionality in PHP applications. When the enchant_broker_request_dict function processes these requests, it fails to properly validate the number of dictionaries being requested or the memory allocation required for each dictionary, leading to a situation where the heap memory allocation becomes corrupted. The buffer overflow specifically occurs in the heap memory management portion of the enchant extension, where the system attempts to allocate memory for dictionary structures without proper bounds checking. This flaw allows attackers to overwrite adjacent memory locations, potentially corrupting critical data structures such as pointers, return addresses, or other control flow information within the application's memory space. The vulnerability's impact is amplified by the fact that the enchant extension is commonly enabled in PHP installations, particularly those running web applications that utilize spell checking or text processing functionality, making it an attractive target for remote code execution attacks.
The operational impact of CVE-2014-9705 extends beyond simple memory corruption, as it enables remote attackers to execute arbitrary code on vulnerable systems with the privileges of the PHP process. This means that an attacker who successfully exploits this vulnerability could gain complete control over the web server hosting vulnerable PHP applications, potentially leading to data breaches, service disruption, or further lateral movement within the network infrastructure. The vulnerability's exploitation requires remote access to a PHP application that utilizes the enchant extension, making it particularly dangerous in web-facing environments where applications may be exposed to untrusted input from external users. The attack vector is specifically tied to spell checking functionality, which is often used in web forms, content management systems, and other user input processing components, providing multiple potential entry points for exploitation. Organizations running vulnerable PHP versions are at significant risk, as the vulnerability can be exploited through simple HTTP requests containing maliciously crafted spell checking parameters, making the attack surface relatively broad and the exploitation process straightforward for skilled attackers. This vulnerability aligns with ATT&CK technique T1190, which involves using vulnerabilities in software to execute arbitrary code, and T1059, which covers command and scripting interpreters, as the exploitation ultimately results in code execution within the PHP interpreter's context.
Organizations affected by CVE-2014-9705 should immediately implement mitigations including upgrading to patched PHP versions, specifically PHP 5.4.38, 5.5.22, or 5.6.6 respectively, which contain the necessary fixes for the heap-based buffer overflow. The most effective mitigation strategy involves applying the official security patches provided by the PHP development team, as these patches address the root cause of the vulnerability by implementing proper bounds checking and memory allocation validation within the enchant_broker_request_dict function. Additionally, administrators should consider disabling the enchant extension entirely if spell checking functionality is not required for their applications, as this eliminates the attack surface associated with this vulnerability. Network-level mitigations such as implementing web application firewalls and input validation controls can provide additional protection by filtering out suspicious requests that attempt to trigger the vulnerable code path. Security monitoring should focus on detecting unusual patterns in spell checking requests or unexpected memory allocation behavior within PHP processes, as these may indicate attempted exploitation attempts. The vulnerability also underscores the importance of regular security assessments and patch management programs, as it demonstrates how seemingly minor extension functionality can present critical security risks when not properly validated against memory safety standards. Organizations should also consider implementing runtime protections such as address space layout randomization and stack canaries to make exploitation more difficult even if patches are not immediately available.