CVE-2016-1740 in iOS
Summary
by MITRE
FontParser in Apple iOS before 9.3, OS X before 10.11.4, tvOS before 9.2, and watchOS before 2.2 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via a crafted PDF document.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability identified as CVE-2016-1740 represents a critical memory corruption flaw within Apple's FontParser component that affected multiple operating systems including iOS, macOS, tvOS, and watchOS. This vulnerability resides in the font parsing functionality that processes font data within PDF documents, creating a remote code execution vector that could be exploited by attackers who craft malicious PDF files. The flaw specifically affects versions prior to iOS 9.3, OS X 10.11.4, tvOS 9.2, and watchOS 2.2, indicating a widespread impact across Apple's ecosystem. The vulnerability is classified under CWE-125 as an out-of-bounds read condition that occurs when the FontParser fails to properly validate font data structures, leading to memory corruption that can be leveraged for arbitrary code execution.
The technical exploitation of this vulnerability occurs when a malicious PDF document containing specially crafted font data is opened by an affected system. The FontParser component attempts to parse font information within the PDF, but due to insufficient bounds checking and input validation, it processes malformed font data that triggers a memory corruption condition. This memory corruption can be manipulated by attackers to overwrite critical memory locations, potentially allowing them to inject and execute arbitrary code with the privileges of the affected application. The attack vector is particularly concerning because PDF documents are commonly encountered in email attachments, web downloads, and file sharing scenarios, making the exploit surface extremely wide. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1203 for exploitation for execution, as it enables attackers to achieve code execution through document-based attacks.
The operational impact of CVE-2016-1740 extends beyond simple remote code execution to include potential denial of service conditions that can crash affected systems. When exploited, the memory corruption can cause applications to crash or become unresponsive, effectively creating a denial of service scenario that disrupts normal system operations. The vulnerability's ability to execute arbitrary code makes it particularly dangerous in enterprise environments where attackers could gain unauthorized access to sensitive systems, potentially leading to data breaches, privilege escalation, and persistent access to compromised networks. The widespread nature of the affected platforms means that organizations using Apple products across multiple device types face significant risk exposure. Organizations should consider the vulnerability's impact on their security posture and implement appropriate mitigations to protect against potential exploitation attempts.
The remediation for CVE-2016-1740 requires immediate deployment of Apple's security updates that address the font parsing vulnerability in the affected operating system versions. System administrators should prioritize patching all affected devices across iOS, macOS, tvOS, and watchOS platforms to prevent exploitation attempts. Additional mitigations include implementing email filtering solutions that scan PDF attachments for malicious content, disabling automatic PDF viewing in web browsers, and educating users about the risks of opening PDF documents from untrusted sources. Security monitoring should include detection of unusual PDF processing activities and potential exploitation attempts. The vulnerability's classification as a memory corruption issue emphasizes the need for robust input validation and bounds checking in font parsing libraries. Organizations should also consider implementing network segmentation and endpoint protection solutions that can detect and prevent exploitation attempts targeting this specific vulnerability.