CVE-2016-6289 in macOS
Summary
by MITRE
Integer overflow in the virtual_file_ex function in TSRM/tsrm_virtual_cwd.c in PHP before 5.5.38, 5.6.x before 5.6.24, and 7.x before 7.0.9 allows remote attackers to cause a denial of service (stack-based buffer overflow) or possibly have unspecified other impact via a crafted extract operation on a ZIP archive.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability CVE-2016-6289 represents a critical integer overflow flaw within PHP's file handling mechanisms that affects multiple versions of the PHP runtime environment. This issue resides in the virtual_file_ex function located in TSRM/tsrm_virtual_cwd.c, which is part of PHP's Thread Safe Resource Manager component responsible for managing virtual file system operations. The vulnerability specifically manifests when processing ZIP archive extraction operations, making it particularly dangerous in web applications that handle user-uploaded archives or perform automated archive processing.
The technical nature of this flaw stems from improper integer overflow handling during the virtual file system operations that occur when extracting files from ZIP archives. When PHP processes a crafted ZIP archive with maliciously constructed file entries, the virtual_file_ex function fails to properly validate integer values used for buffer allocation and file size calculations. This leads to a stack-based buffer overflow condition where the application attempts to write data beyond the allocated memory boundaries, potentially corrupting adjacent memory regions and causing unpredictable behavior.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable more severe exploitation scenarios. Remote attackers can leverage this vulnerability to cause application crashes through stack-based buffer overflows, leading to service disruption and denial of service attacks against web applications. Additionally, the unspecified other impacts mentioned in the vulnerability description suggest potential for more sophisticated exploitation techniques that could allow attackers to execute arbitrary code or bypass security controls, making this a particularly concerning flaw in web application environments where ZIP archive processing is common.
The vulnerability affects PHP versions prior to specific security patches, including PHP 5.5.38, 5.6.24, and 7.0.9, indicating that this flaw existed across multiple major PHP release lines and would have impacted a substantial portion of web applications running on the platform. Organizations utilizing PHP-based web applications that process user-uploaded ZIP files or perform automated archive extraction operations would be particularly vulnerable to this attack vector. The flaw aligns with CWE-190, which specifically addresses integer overflow conditions, and represents a classic example of how improper input validation can lead to memory corruption vulnerabilities.
Mitigation strategies for this vulnerability require immediate patching of affected PHP installations to the recommended secure versions, as well as implementing additional defensive measures to reduce the attack surface. Organizations should disable ZIP archive processing functionality in web applications where possible, implement strict file type validation for uploaded archives, and establish monitoring for suspicious file extraction activities. The ATT&CK framework categorizes this vulnerability under privilege escalation and denial of service techniques, as attackers can leverage it to disrupt services or potentially gain elevated privileges within the application environment. Regular security assessments and vulnerability scanning should be implemented to identify similar integer overflow conditions in custom PHP extensions or third-party libraries that may be vulnerable to analogous attacks.