CVE-2016-4671 in macOS
Summary
by MITRE
An issue was discovered in certain Apple products. macOS before 10.12.1 is affected. The issue involves the "ImageIO" component. It allows remote attackers to execute arbitrary code or cause a denial of service (out-of-bounds write and application crash) via a crafted PDF file.
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Analysis
by VulDB Data Team • 09/28/2022
The vulnerability identified as CVE-2016-4671 represents a critical security flaw within Apple's macOS operating system affecting versions prior to 10.12.1. This issue resides within the ImageIO framework, which serves as a core component responsible for processing various image formats including PDF documents. The flaw manifests when the system attempts to parse maliciously crafted PDF files, creating a pathway for remote attackers to exploit the system through crafted input that triggers unexpected behavior in the underlying image processing pipeline.
The technical nature of this vulnerability stems from improper bounds checking within the ImageIO component's PDF parsing implementation. When a specially crafted PDF file is processed, the system encounters an out-of-bounds write condition that occurs during the handling of specific image data structures embedded within the document. This memory corruption vulnerability enables attackers to manipulate the program's execution flow and potentially execute arbitrary code with the privileges of the affected application. The vulnerability's classification aligns with CWE-129, which addresses insufficient validation of length of input buffers, and specifically relates to CWE-787, representing out-of-bounds write conditions that can lead to arbitrary code execution.
From an operational perspective, this vulnerability presents significant risk to macOS users since PDF files are commonly encountered in email attachments, web downloads, and shared documents across various business and personal environments. Attackers can leverage this flaw by delivering malicious PDF files through spear-phishing campaigns or compromised websites, where simply opening the document in a PDF viewer or when the system processes it for thumbnail generation can trigger the exploit. The potential impact includes complete system compromise, data exfiltration, and persistent backdoor installation, making this vulnerability particularly dangerous in enterprise environments where macOS systems may be targeted by sophisticated threat actors.
The security implications extend beyond immediate code execution capabilities as this vulnerability demonstrates the broader risks associated with image processing libraries in operating systems. The flaw exemplifies how seemingly benign functionality can become a vector for sophisticated attacks, particularly when dealing with complex file format parsing. Organizations should consider implementing network-level protections such as PDF sandboxing, content filtering, and email security solutions to mitigate exposure while awaiting official patches. Additionally, the vulnerability highlights the importance of timely security updates and proper patch management processes, as the issue was resolved through Apple's security updates for macOS 10.12.1 and subsequent releases.
According to ATT&CK framework methodology, this vulnerability maps to multiple techniques including T1059 for command and control through arbitrary code execution, T1190 for exploitation of remote services, and T1070 for indicator removal. The attack chain typically involves initial compromise through phishing or web-based delivery, followed by exploitation of the ImageIO vulnerability to establish persistent access. Security practitioners should implement monitoring for unusual PDF processing activities and establish incident response procedures specifically addressing this type of memory corruption vulnerability. The remediation approach requires immediate deployment of Apple's security patches, along with network segmentation and endpoint protection measures to prevent exploitation attempts.