CVE-2016-4345 in PHP
Summary
by MITRE
Integer overflow in the php_filter_encode_url function in ext/filter/sanitizing_filters.c in PHP before 7.0.4 allows remote attackers to cause a denial of service or possibly have unspecified other impact via a long string, leading to a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 07/27/2022
The vulnerability identified as CVE-2016-4345 represents a critical integer overflow flaw within PHP's filter extension, specifically affecting the php_filter_encode_url function located in ext/filter/sanitizing_filters.c. This issue exists in PHP versions prior to 7.0.4 and demonstrates how improper input validation can lead to severe security consequences. The vulnerability stems from insufficient bounds checking when processing URL encoding operations, creating a scenario where maliciously crafted input can trigger unexpected behavior in the application's memory management.
The technical exploitation of this vulnerability occurs when a remote attacker submits a particularly long string to the php_filter_encode_url function, which then processes this input without adequate overflow protection. The integer overflow condition causes the function to miscalculate buffer sizes, ultimately resulting in a heap-based buffer overflow. This memory corruption vulnerability allows attackers to manipulate heap memory structures in ways that can lead to arbitrary code execution or denial of service conditions. The flaw operates at the core level of PHP's input sanitization mechanisms, making it particularly dangerous as it can affect any application that relies on URL encoding functionality.
From an operational impact perspective, this vulnerability creates significant risks for web applications running affected PHP versions. The heap-based buffer overflow can manifest in multiple ways including application crashes, memory corruption, or potentially more severe outcomes such as remote code execution. The denial of service aspect directly impacts availability, while the potential for unspecified other impacts suggests the possibility of privilege escalation or data compromise. Organizations using vulnerable PHP installations face substantial risk as attackers can leverage this flaw to disrupt services or gain unauthorized access to systems. The vulnerability's exploitation requires minimal privileges and can be executed remotely, making it particularly attractive to threat actors seeking to compromise web applications.
The remediation strategy for this vulnerability centers on upgrading to PHP version 7.0.4 or later, where the integer overflow has been properly addressed through enhanced input validation and buffer size calculations. Additionally, administrators should implement proper input sanitization at application level, validate all user-supplied data before processing, and consider implementing web application firewalls to detect and block malicious input patterns. Organizations should also conduct thorough security assessments of their PHP applications to identify potential exploitation vectors and ensure all systems are updated with the latest security patches. This vulnerability aligns with CWE-190, which describes integer overflow conditions, and may map to ATT&CK technique T1203, involving the exploitation of software vulnerabilities for privilege escalation or denial of service.
The broader implications of this vulnerability highlight the importance of robust memory management practices in server-side scripting languages and underscore the necessity of regular security updates. Legacy PHP installations remain particularly vulnerable to such issues, emphasizing the critical need for organizations to maintain current software versions and implement comprehensive patch management strategies. The vulnerability serves as a reminder that even fundamental functions like URL encoding can contain critical security flaws when proper overflow protections are not implemented, making it essential for developers to follow secure coding practices and conduct thorough code reviews for memory-related operations.