CVE-2005-0524 in Mac OS X
Summary
by MITRE
The php_handle_iff function in image.c for PHP 4.2.2, 4.3.9, 4.3.10 and 5.0.3, as reachable by the getimagesize PHP function, allows remote attackers to cause a denial of service (infinite loop) via a -8 size value.
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Analysis
by VulDB Data Team • 03/11/2021
The vulnerability identified as CVE-2005-0524 represents a critical denial of service flaw within the PHP image processing subsystem. This weakness specifically affects PHP versions 4.2.2, 4.3.9, 4.3.10, and 5.0.3, where the php_handle_iff function in the image.c file becomes susceptible to malicious input during image size detection operations. The vulnerability manifests when the getimagesize PHP function processes specially crafted image files that contain a -8 size value, creating a condition that leads to an infinite loop in the processing logic. This flaw resides in the image format handling mechanism that is commonly used in web applications for image validation and processing, making it particularly dangerous in web server environments where PHP handles user-uploaded content.
The technical implementation of this vulnerability stems from inadequate input validation within the image parsing routine. When the php_handle_iff function encounters a negative size value of -8 in an image file header, it fails to properly validate the input parameter before proceeding with the image processing calculations. This lack of proper boundary checking causes the function to enter an infinite loop as it attempts to process the malformed data, consuming system resources indefinitely. The flaw can be categorized under CWE-835, which specifically addresses infinite loops in software implementations, where the loop control variable fails to progress toward termination. The vulnerability is particularly concerning because it operates at the core image processing layer, meaning any application using PHP's getimagesize function to validate uploaded images becomes vulnerable to this attack vector.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited by remote attackers to exhaust server resources and cause system-wide denial of service conditions. Attackers can craft malicious image files with the specific -8 size value and upload them to web applications that utilize PHP's image processing capabilities, leading to sustained resource consumption and potential system crashes. This vulnerability is particularly dangerous in multi-user environments where multiple concurrent requests can be simultaneously consumed by the infinite loop, effectively bringing the entire web application to a halt. The attack requires minimal technical expertise to execute, making it a preferred method for denial of service attacks against PHP-based web servers. According to ATT&CK framework, this vulnerability maps to T1499.004, which covers Network Denial of Service, and T1595.001, which addresses reconnaissance through network scanning.
Mitigation strategies for this vulnerability require immediate patching of affected PHP versions, as the flaw was addressed in subsequent releases through proper input validation and boundary checking mechanisms. System administrators should prioritize updating their PHP installations to versions that contain the necessary fixes, typically PHP 4.3.11, 4.4.0, or 5.0.4 and later. Additionally, implementing input validation at the application level can provide an additional layer of protection by sanitizing image file parameters before passing them to PHP's getimagesize function. Network-level protections such as rate limiting and resource monitoring can help detect and prevent exploitation attempts, while proper file type validation and size restrictions should be implemented to reduce the attack surface. Organizations should also consider implementing intrusion detection systems that can identify unusual resource consumption patterns associated with infinite loop exploitation attempts. The vulnerability demonstrates the importance of proper input validation in image processing libraries and serves as a reminder of the critical security considerations that must be addressed in multimedia handling components of web applications.