CVE-2016-4629 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 crafted xStride and yStride values in an EXR image.
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Analysis
by VulDB Data Team • 09/06/2022
The vulnerability identified as CVE-2016-4629 represents a critical memory corruption flaw within Apple's ImageIO framework affecting macOS versions prior to 10.11.6. This vulnerability specifically targets the handling of EXR (OpenEXR) image files, which are commonly used in professional imaging and visual effects applications. The flaw manifests when the system processes crafted xStride and yStride values within EXR image metadata, creating conditions that can lead to arbitrary code execution or system denial of service. The vulnerability operates at the intersection of image processing libraries and memory management, making it particularly dangerous as it can be triggered through routine image file handling operations.
The technical implementation of this vulnerability stems from insufficient bounds checking and validation within the ImageIO framework's EXR parser. When processing EXR images, the system fails to properly validate the stride parameters that define the spacing between pixels in different dimensions. Attackers can craft malicious EXR files containing malformed xStride and yStride values that, when processed by the vulnerable ImageIO framework, result in memory corruption. This memory corruption can manifest as buffer overflows or pointer arithmetic errors that allow attackers to manipulate memory layout and potentially execute arbitrary code. The vulnerability is classified under CWE-129 as "Improper Validation of Array Index" and also relates to CWE-787 as "Out-of-bounds Write" within the context of image processing memory management.
The operational impact of CVE-2016-4629 extends beyond simple denial of service scenarios to encompass full system compromise capabilities. Attackers exploiting this vulnerability can leverage the memory corruption to execute arbitrary code with the privileges of the affected process, which typically runs with user-level privileges but could potentially be escalated. The vulnerability affects both local and remote attack vectors, as EXR files can be delivered through various means including web browsing, email attachments, or file sharing systems. This makes the vulnerability particularly dangerous in enterprise environments where users may unknowingly process malicious image files. The ATT&CK framework categorizes this vulnerability under T1059.007 for "Command and Scripting Interpreter: JavaScript" and T1203 for "Exploitation for Client Execution" when considering how attackers might leverage it to deliver payloads through image files.
Mitigation strategies for CVE-2016-4629 primarily focus on immediate system updates and operational security measures. Apple addressed this vulnerability through macOS 10.11.6 security updates that included enhanced bounds checking and validation routines within the ImageIO framework. Organizations should prioritize immediate deployment of these updates across all affected systems, particularly those handling untrusted image files or operating in high-risk environments. Additional defensive measures include implementing strict file type validation for image files, deploying sandboxing solutions that limit the impact of potential exploitation, and monitoring for unusual image processing activities that might indicate exploitation attempts. Network-based mitigations such as content filtering and email scanning can help prevent delivery of malicious EXR files, while endpoint detection and response solutions should monitor for suspicious memory allocation patterns that could indicate exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date security patches and demonstrates the critical nature of image processing libraries in modern operating systems, where seemingly benign file format handling can become a vector for sophisticated attacks.