CVE-2016-1790 in iOS
Summary
by MITRE
Buffer overflow in the Accessibility component in Apple iOS before 9.3.2 allows attackers to obtain sensitive kernel memory-layout information via a crafted app.
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Analysis
by VulDB Data Team • 08/21/2022
The vulnerability identified as CVE-2016-1790 represents a critical buffer overflow flaw within Apple's Accessibility component in iOS versions prior to 9.3.2. This security weakness resides in the way the operating system handles memory operations within its accessibility services, creating an exploitable condition that can be leveraged by malicious actors. The issue specifically affects the kernel memory layout disclosure mechanism, which provides attackers with sensitive information about the system's internal memory organization. Such information is invaluable for advanced exploitation techniques as it enables attackers to bypass modern memory protection mechanisms like stack canaries, address space layout randomization, and other security features designed to prevent exploitation.
The technical implementation of this vulnerability stems from improper bounds checking within the Accessibility component's memory handling routines. When a crafted application attempts to interact with the accessibility services, it can trigger a buffer overflow condition that overwrites adjacent memory locations. This overflow specifically targets kernel memory regions where the system maintains critical layout information about memory segments, heap structures, and process mappings. The vulnerability manifests through the manipulation of accessibility APIs that are designed to assist users with disabilities but can be abused to gain unauthorized access to kernel memory structures. The flaw falls under CWE-121, which categorizes buffer overflow conditions that occur when insufficient bounds checking allows memory to be overwritten beyond allocated buffers, and specifically relates to the improper handling of memory in kernel space components.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with crucial kernel memory layout data that can be used for subsequent exploitation attempts. This type of information disclosure is particularly dangerous because it enables attackers to perform advanced exploitation techniques such as return-oriented programming attacks, heap spraying, and other sophisticated methods that require detailed knowledge of memory organization. The vulnerability affects all iOS devices running versions before 9.3.2, making it a widespread concern across the Apple ecosystem. Attackers can leverage this information to craft more effective exploits against other vulnerabilities present in the system, creating a dangerous chain reaction that can lead to complete system compromise. This vulnerability aligns with ATT&CK technique T1059 which involves using system services and APIs to gain unauthorized access to system resources, and T1068 which focuses on exploiting vulnerabilities in system components.
The mitigation strategy for CVE-2016-1790 centers on updating to iOS 9.3.2 or later versions, which contain patches that address the buffer overflow condition in the Accessibility component. Apple's security update resolves the improper memory handling by implementing proper bounds checking and memory validation routines within the accessibility services. Organizations should also implement monitoring for suspicious application behavior that might attempt to exploit this vulnerability, particularly in environments where iOS devices are used in sensitive contexts. The patch addresses the root cause by ensuring that all memory operations within the accessibility component properly validate buffer sizes before performing memory writes, preventing the overflow condition that previously allowed memory layout information disclosure. Additionally, system administrators should consider implementing application whitelisting policies that restrict the execution of potentially malicious applications that might attempt to exploit this vulnerability. The fix demonstrates Apple's adherence to security best practices by implementing robust input validation and memory management controls that prevent similar buffer overflow conditions from occurring in the future, aligning with industry standards for secure coding practices and vulnerability remediation.