CVE-2016-4660 in watchOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 10.1 is affected. macOS before 10.12.1 is affected. tvOS before 10.0.1 is affected. watchOS before 3.1 is affected. The issue involves the "FontParser" component. It allows remote attackers to obtain sensitive information or cause a denial of service (out-of-bounds read and application crash) via a crafted font.
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Analysis
by VulDB Data Team • 09/28/2022
The vulnerability identified as CVE-2016-4660 represents a critical security flaw within Apple's font parsing infrastructure affecting multiple operating systems including iOS, macOS, tvOS, and watchOS. This issue resides within the FontParser component which is responsible for processing font files and rendering text across Apple's ecosystem. The vulnerability stems from inadequate bounds checking during font file parsing operations, creating a scenario where maliciously crafted font files can trigger unexpected behavior in the underlying system. The flaw specifically manifests as an out-of-bounds read condition that occurs when the parser attempts to access memory locations beyond the allocated buffer boundaries while processing malformed font data. This fundamental parsing error creates multiple attack vectors that can be exploited by remote adversaries to either extract sensitive information from system memory or to deliberately crash applications and system processes.
The technical nature of this vulnerability aligns with CWE-125, which describes out-of-bounds read conditions in software systems, and demonstrates how insufficient input validation can lead to serious security consequences. The FontParser component's failure to properly validate font file structures means that attackers can craft specially designed font files that contain malicious data sequences. When these crafted fonts are processed by the system, the parser attempts to read memory locations that do not correspond to legitimate font data, resulting in either information disclosure or system instability. The out-of-bounds read vulnerability allows attackers to potentially access sensitive data residing in adjacent memory locations, which could include cryptographic keys, user credentials, or other confidential information stored in system memory. Additionally, the same parsing error can be exploited to trigger application crashes through controlled memory access patterns that force the system to terminate processes unexpectedly.
The operational impact of CVE-2016-4660 extends beyond simple denial of service scenarios to encompass potential information disclosure risks that could compromise user privacy and system security. Attackers can leverage this vulnerability through various attack vectors including malicious email attachments, compromised websites, or even through malicious applications that display crafted fonts. The remote exploitation capability means that adversaries do not require physical access to devices or elevated privileges to carry out successful attacks. When exploited, the vulnerability can cause applications to crash or freeze, disrupting user experience and potentially leading to more severe consequences depending on the application being targeted. The widespread nature of font rendering across Apple's operating systems means that the attack surface is extensive, affecting not only core system applications but also third-party software that relies on standard font processing capabilities. This vulnerability particularly impacts the security posture of Apple devices because font files are commonly encountered in everyday usage scenarios, making the attack surface highly accessible to potential threat actors.
Mitigation strategies for CVE-2016-4660 primarily focus on applying the official security updates released by Apple as part of their regular patching cycle. Users should immediately install the corresponding software updates for their affected operating systems, which include iOS 10.1, macOS 10.12.1, tvOS 10.0.1, and watchOS 3.1. These updates contain patched versions of the FontParser component that implement proper bounds checking and input validation mechanisms. Organizations should also consider implementing additional security measures such as network-based font filtering, email attachment scanning, and application whitelisting to reduce the risk of exploitation. The vulnerability demonstrates the importance of proper input validation and memory safety practices in system components that process untrusted data, aligning with ATT&CK technique T1059.007 for process injection and T1557.001 for local network sniffing that could be used in conjunction with such vulnerabilities. Security teams should also monitor for indicators of compromise related to font file processing and implement proper logging and monitoring of font-related system calls to detect potential exploitation attempts. The incident underscores the critical need for robust security testing of input processing components and highlights the necessity of maintaining up-to-date security patches across all system components to prevent exploitation of similar vulnerabilities in the future.