CVE-2016-4346 in PHP
Summary
by MITRE
Integer overflow in the str_pad function in ext/standard/string.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.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 07/27/2022
The vulnerability identified as CVE-2016-4346 represents a critical integer overflow flaw within PHP's string manipulation capabilities that has significant implications for web application security. This vulnerability exists in the str_pad function located in the ext/standard/string.c file of PHP versions prior to 7.0.4, making it a persistent threat in legacy systems that have not been properly updated. The flaw manifests when the function processes excessively long strings, creating conditions where integer arithmetic operations overflow beyond their designated memory boundaries. This vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, which is a well-documented weakness in software security that occurs when an integer value exceeds its maximum representable value and wraps around to a smaller value. The specific nature of this vulnerability aligns with the ATT&CK technique T1499.004 which involves network denial of service attacks, as the vulnerability can be exploited to cause system instability through heap-based buffer overflow conditions.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious input string that, when processed by the str_pad function, triggers an integer overflow condition. This overflow causes the function to allocate insufficient memory for the resulting string, leading to heap corruption that can manifest as heap-based buffer overflow. The vulnerability is particularly dangerous because it can be triggered through user-supplied input that passes through the str_pad function, making it accessible via web applications that accept and process user data. When the integer overflow occurs, the system may attempt to allocate memory blocks that are either too small or too large, creating memory corruption that can lead to application crashes, denial of service conditions, or potentially more severe consequences depending on the execution environment. The heap-based nature of the overflow means that the corruption affects the program's dynamic memory allocation system, which can result in unpredictable behavior and system instability.
The operational impact of CVE-2016-4346 extends beyond simple denial of service scenarios, as the vulnerability creates potential pathways for more sophisticated attacks that could leverage the heap corruption for code execution or privilege escalation. Web applications that utilize PHP and process user input through str_pad functions become prime targets for exploitation, particularly in environments where input validation is insufficient or nonexistent. The vulnerability's potential for unspecified other impacts means that attackers could potentially use the heap corruption to manipulate program execution flow, leading to data breaches, system compromise, or unauthorized access to sensitive information. Organizations running affected PHP versions face significant risk exposure, especially in environments where multiple applications depend on string manipulation functions that could be leveraged by attackers to exploit this vulnerability. The vulnerability's presence in the core string handling functions of PHP means that the attack surface is extensive, as virtually any web application that processes user input could be vulnerable to exploitation.
Mitigation strategies for CVE-2016-4346 primarily focus on immediate remediation through PHP version upgrades to 7.0.4 or later, which contain the necessary patches to address the integer overflow condition. Organizations should implement comprehensive patch management processes to ensure all affected systems are updated promptly, as this vulnerability has been widely documented and exploited in the wild. Additionally, input validation and sanitization measures should be strengthened to prevent malicious input from reaching vulnerable functions, though this approach alone is insufficient as the vulnerability exists at the core library level. Security monitoring should include detection of unusual memory allocation patterns and potential denial of service conditions that might indicate exploitation attempts. The vulnerability's classification under CWE-190 and its potential for heap-based buffer overflow make it a high-priority target for security teams to address through both immediate patching and long-term code review processes to identify similar integer overflow vulnerabilities in custom application code and third-party libraries.