CVE-2016-7627 in watchOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 10.2 is affected. macOS before 10.12.2 is affected. watchOS before 3.1.3 is affected. The issue involves the "CoreGraphics" component. It allows attackers to cause a denial of service (NULL pointer dereference and application crash) via a crafted font.
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Analysis
by VulDB Data Team • 11/03/2022
The vulnerability identified as CVE-2016-7627 represents a critical flaw within Apple's CoreGraphics framework that affected multiple operating systems including iOS, macOS, and watchOS. This security issue stems from improper handling of crafted font files within the graphics rendering subsystem, creating a pathway for attackers to exploit the system through maliciously constructed font data. The vulnerability specifically manifests as a NULL pointer dereference condition that occurs when the CoreGraphics component processes malformed font files, leading to application crashes and potential denial of service scenarios across affected Apple platforms.
The technical nature of this vulnerability places it squarely within CWE-476, which defines NULL pointer dereference as a condition where a null value is dereferenced, resulting in system instability and application termination. The flaw exists in how the CoreGraphics framework handles font parsing operations, particularly when encountering specially crafted font files that contain malformed or unexpected data structures. When these malicious fonts are processed by applications that utilize CoreGraphics for text rendering, the system attempts to access memory locations that have not been properly initialized, resulting in immediate application crashes and system instability. This vulnerability demonstrates the inherent risks associated with font processing in graphics frameworks, where the parsing of untrusted input data can lead to critical system failures.
The operational impact of CVE-2016-7627 extends beyond simple application crashes to potentially enable broader attack vectors that could compromise system availability and user experience across Apple's ecosystem. Attackers can leverage this vulnerability to cause denial of service conditions in applications that rely on CoreGraphics for rendering text and graphics, effectively disrupting normal system operations and potentially creating opportunities for more sophisticated attacks. The affected versions include iOS before 10.2, macOS before 10.12.2, and watchOS before 3.1.3, representing a substantial portion of Apple's deployed user base at the time of discovery. This vulnerability aligns with ATT&CK technique T1499.004, which describes denial of service attacks targeting application availability through exploitation of software vulnerabilities.
Mitigation strategies for this vulnerability primarily focus on prompt system updates and patches provided by Apple to address the underlying CoreGraphics implementation flaws. Users should immediately apply the security updates released by Apple for their respective operating systems, as these patches contain fixes for the font parsing logic that prevents the NULL pointer dereference condition. System administrators should prioritize deployment of these updates across enterprise environments to prevent potential exploitation. Additional defensive measures include implementing application sandboxing and restricting font file processing in high-security environments, though the most effective approach remains timely patch management. The vulnerability highlights the importance of robust input validation in graphics processing libraries and demonstrates how seemingly benign components like font rendering can become attack surfaces when not properly secured against malformed input data.