CVE-2015-4605 in PHP
Summary
by MITRE
The mcopy function in softmagic.c in file 5.x, as used in the Fileinfo component in PHP before 5.4.40, 5.5.x before 5.5.24, and 5.6.x before 5.6.8, does not properly restrict a certain offset value, which allows remote attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted string that is mishandled by a "Python script text executable" rule.
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Analysis
by VulDB Data Team • 05/22/2022
The vulnerability identified as CVE-2015-4605 represents a critical security flaw in the file command's magic file processing functionality, specifically within the mcopy function located in softmagic.c of file version 5.x. This vulnerability affects PHP versions prior to 5.4.40, 5.5.24, and 5.6.8, where the Fileinfo component fails to properly validate offset values during magic file processing. The issue stems from inadequate input sanitization and validation mechanisms that allow maliciously crafted strings to bypass normal processing boundaries. When a specially crafted string is processed through the "Python script text executable" rule, the mcopy function's improper handling of offset values creates a condition where memory access violations can occur. This flaw manifests as either a denial of service through application crashes or potentially more severe arbitrary code execution depending on the specific memory corruption patterns. The vulnerability operates at the intersection of file type detection and memory management, where the magic file database parsing process fails to enforce proper bounds checking on offset parameters.
The technical implementation of this vulnerability involves the manipulation of offset values within the mcopy function which is responsible for copying data from one location to another during magic file processing. When PHP processes file type detection through the Fileinfo extension, it relies on magic files that contain rules for identifying different file types based on their content patterns. The specific "Python script text executable" rule in the magic database contains a flaw where it does not properly validate the offset parameter before passing it to the mcopy function. This allows attackers to provide an offset value that exceeds the bounds of the allocated memory region, causing buffer overflows or memory corruption. The vulnerability is categorized under CWE-121 as a stack-based buffer overflow, though it can manifest as heap-based issues depending on the memory layout. The flaw represents a classic case of improper input validation where the system fails to check boundary conditions before performing memory operations, creating a pathway for malicious data to trigger unintended behavior.
The operational impact of CVE-2015-4605 extends beyond simple denial of service to potentially enable remote code execution, making it a significant threat to web applications that utilize PHP's Fileinfo functionality. Attackers can exploit this vulnerability by uploading or processing files that contain specially crafted strings designed to trigger the vulnerable code path during magic file evaluation. The vulnerability is particularly dangerous in web environments where user-supplied files are processed for type detection, as it can be leveraged to crash web servers or potentially execute arbitrary code on the target system. This creates a scenario where legitimate file processing operations can be weaponized to compromise system integrity. The vulnerability affects PHP's Fileinfo component which is widely used for file type detection in various web applications, making it a prime target for exploitation. The potential for remote code execution means that successful exploitation could allow attackers to gain full control over the affected system, especially when combined with other vulnerabilities or when the web server has elevated privileges.
Mitigation strategies for CVE-2015-4605 should prioritize immediate patching of affected PHP versions to the latest stable releases that contain the necessary fixes for the mcopy function's offset validation. Organizations should implement comprehensive input validation and sanitization measures for all file processing operations, particularly those involving user-supplied content. The recommended approach includes upgrading to PHP versions 5.4.40, 5.5.24, or 5.6.8, which contain the patched implementation of the mcopy function with proper offset validation. Additionally, implementing proper security monitoring and intrusion detection systems can help identify exploitation attempts by monitoring for unusual file processing patterns or memory access violations. Network segmentation and application firewalls should be configured to limit access to file processing endpoints, while implementing strict file type validation and content filtering mechanisms. Organizations should also consider implementing the principle of least privilege for web server processes and regularly audit their file handling code for similar validation issues. The ATT&CK framework categorizes this vulnerability under T1059 for command and script injection, as the exploitation may involve injection of malicious code through crafted file content, making it important to monitor for such activities in system logs and network traffic.