CVE-2016-5770 in macOS
Summary
by MITRE
Integer overflow in the SplFileObject::fread function in spl_directory.c in the SPL extension in PHP before 5.5.37 and 5.6.x before 5.6.23 allows remote attackers to cause a denial of service or possibly have unspecified other impact via a large integer argument, a related issue to CVE-2016-5096.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability identified as CVE-2016-5770 represents a critical integer overflow flaw within PHP's Standard PHP Library extension, specifically affecting the SplFileObject::fread function implementation in spl_directory.c. This issue impacts PHP versions prior to 5.5.37 and 5.6.x versions before 5.6.23, creating a potential pathway for remote attackers to exploit the system through carefully crafted integer arguments. The vulnerability stems from insufficient input validation and overflow handling within the file reading operations, where large integer values can cause the underlying integer arithmetic to wrap around, leading to unpredictable behavior. The flaw is categorized under CWE-190, which specifically addresses integer overflow conditions that can result in memory corruption or arbitrary code execution, making it a significant concern for systems relying on PHP's file handling capabilities.
The technical exploitation of this vulnerability occurs when an attacker provides a large integer argument to the SplFileObject::fread function, which then triggers the integer overflow during internal arithmetic operations. This overflow can cause the function to allocate insufficient memory or perform invalid memory access patterns, resulting in system instability or potential code execution. The vulnerability's relationship to CVE-2016-5096 indicates a broader pattern of integer overflow issues within PHP's SPL extension, suggesting that developers may have overlooked comprehensive input validation across multiple file handling functions. Attackers can leverage this weakness to cause denial of service by exhausting system resources or potentially execute arbitrary code if the overflow leads to memory corruption that can be controlled by malicious inputs.
The operational impact of CVE-2016-5770 extends beyond simple denial of service scenarios, as the integer overflow can create conditions where attackers might manipulate memory layout or execute code with elevated privileges. Systems using PHP applications that process untrusted file data through SplFileObject operations become particularly vulnerable, especially web applications that handle file uploads or stream processing. The vulnerability can be exploited through various attack vectors including web applications, command-line scripts, or any PHP environment where file reading operations are performed with user-supplied input. Organizations running affected PHP versions face significant risk as the overflow can potentially be chained with other vulnerabilities to create more severe exploitation scenarios, making the impact of this single vulnerability much broader than initially apparent.
Mitigation strategies for CVE-2016-5770 primarily focus on immediate version upgrades to PHP 5.5.37 or 5.6.23, which contain the necessary patches to prevent integer overflow conditions in the SPL extension. System administrators should implement comprehensive patch management procedures to ensure all affected PHP installations are updated promptly, as the vulnerability can be exploited remotely without authentication. Additional protective measures include input validation at application level, where developers should implement bounds checking for file reading operations and sanitize all user-supplied integer values before passing them to SplFileObject::fread functions. Network-level protections such as web application firewalls and intrusion detection systems can help detect and block exploitation attempts, while code reviews should specifically target SPL extension usage to identify potential integer overflow scenarios. The vulnerability's classification under ATT&CK technique T1203 (Exploitation for Client Execution) and CWE-190 emphasizes the need for both preventive measures and runtime monitoring to detect potential exploitation attempts, with organizations implementing continuous vulnerability assessment programs to identify similar issues in custom PHP applications that may not have been patched through standard updates.