CVE-2016-4543 in PHP
Summary
by MITRE
The exif_process_IFD_in_JPEG function in ext/exif/exif.c in PHP before 5.5.35, 5.6.x before 5.6.21, and 7.x before 7.0.6 does not validate IFD sizes, which allows remote attackers to cause a denial of service (out-of-bounds read) or possibly have unspecified other impact via crafted header data.
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Analysis
by VulDB Data Team • 08/22/2022
The vulnerability identified as CVE-2016-4543 represents a critical buffer over-read flaw in PHP's EXIF extension that affects multiple versions of the PHP runtime environment. This vulnerability resides within the exif_process_IFD_in_JPEG function located in the ext/exif/exif.c source file, which is responsible for processing image metadata within JPEG files. The flaw stems from insufficient validation of IFD (Image File Directory) sizes during the parsing of EXIF headers, creating a scenario where maliciously crafted image files can trigger unexpected behavior in the PHP processing pipeline.
The technical exploitation of this vulnerability occurs when PHP attempts to parse JPEG files containing specially crafted EXIF metadata that contains malformed IFD size indicators. When the exif_process_IFD_in_JPEG function encounters these invalid size specifications, it fails to properly validate the boundaries before attempting to read memory locations, resulting in out-of-bounds memory access patterns. This fundamental flaw in input validation creates opportunities for attackers to either cause denial of service conditions through segmentation faults or potentially execute arbitrary code depending on the system configuration and memory layout. The vulnerability aligns with CWE-125, which specifically addresses out-of-bounds read conditions, and represents a classic example of insufficient input validation leading to memory safety issues.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can be leveraged in various attack vectors within web applications that process user-uploaded images. Web applications utilizing PHP's image processing capabilities, particularly those handling file uploads or image manipulation, become vulnerable to remote exploitation when they fail to properly validate uploaded image metadata. Attackers can craft malicious JPEG files with manipulated EXIF headers that trigger the vulnerable code path, potentially leading to server crashes, resource exhaustion, or in more severe cases, remote code execution depending on the underlying system architecture. This vulnerability particularly affects content management systems, image hosting platforms, and any web application that processes user-provided image files without proper sanitization.
Mitigation strategies for CVE-2016-4543 primarily focus on immediate version upgrades to patched PHP releases, specifically PHP 5.5.35, 5.6.21, and 7.0.6, which contain the necessary fixes for the IFD size validation issue. Organizations should also implement additional defensive measures including input validation of uploaded files, mandatory file type checking, and sandboxed processing environments for image metadata. Network-level protections such as web application firewalls can help detect and block malicious image uploads, while runtime monitoring should be implemented to identify potential exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1203 (Exploitation for Client Execution) and T1499 (Endpoint Denial of Service) techniques, as attackers can leverage it to achieve both service disruption and potential code execution within affected systems. The vulnerability also intersects with T1595 (Active Scanning) as attackers may probe systems for vulnerable PHP versions before attempting exploitation, making proper patch management and vulnerability scanning essential defensive measures.