CVE-2016-4630 in Mac OS X
Summary
by MITRE
ImageIO in Apple OS X before 10.11.6 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted EXR image with B44 compression.
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Analysis
by VulDB Data Team • 09/06/2022
The vulnerability identified as CVE-2016-4630 represents a critical memory corruption flaw within Apple's ImageIO framework affecting macOS versions prior to 10.11.6. This issue specifically manifests when processing EXR (OpenEXR) image files that utilize B44 compression algorithms, creating a significant attack surface for remote code execution and denial of service conditions. The flaw resides in how the system handles compressed image data during the decoding process, where improper bounds checking and memory management lead to exploitable conditions that can be triggered through crafted malicious image files.
The technical implementation of this vulnerability stems from inadequate input validation within the ImageIO framework's handling of OpenEXR format files. When the system encounters an EXR image with B44 compression, the decompression routine fails to properly validate the compressed data structure, leading to memory corruption that can be leveraged to overwrite critical memory locations. This memory corruption typically occurs during the decompression phase where the system allocates memory buffers based on estimated sizes derived from the compressed data headers without sufficient validation of the actual data boundaries. The vulnerability maps directly to CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write operations that can result in arbitrary code execution.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as remote attackers can potentially execute arbitrary code on affected systems with the privileges of the user running the vulnerable application. This makes the vulnerability particularly dangerous in environments where users may encounter malicious image files through web browsing, email attachments, or file sharing systems. The attack vector requires minimal user interaction, as simply opening or previewing the malicious EXR file can trigger the exploit, making it highly suitable for social engineering campaigns. The vulnerability affects not only direct image viewing applications but also any software that relies on Apple's ImageIO framework for image processing, including web browsers, design applications, and document viewers.
Mitigation strategies for CVE-2016-4630 primarily focus on applying the official security patches provided by Apple through macOS updates. System administrators should prioritize deployment of macOS 10.11.6 or later versions that contain the necessary fixes for this vulnerability. Additional protective measures include implementing strict file type filtering for image files, particularly in enterprise environments where users may encounter untrusted image content. Network-based protections such as web application firewalls and content filtering systems can help prevent the delivery of malicious EXR files to end users. Organizations should also consider implementing sandboxing mechanisms around image processing applications and monitoring for unusual memory allocation patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of robust input validation in multimedia processing frameworks and aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as exploitation may involve executing code through compromised image processing pipelines. Regular security assessments of image handling components and adherence to secure coding practices for memory management are essential for preventing similar vulnerabilities in future implementations.