CVE-2012-3749 in iOS
Summary
by MITRE
The extensions APIs in the kernel in Apple iOS before 6.0.1 provide kernel addresses in responses that contain an OSBundleMachOHeaders key, which makes it easier for remote attackers to bypass the ASLR protection mechanism via a crafted app.
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Analysis
by VulDB Data Team • 04/18/2021
The vulnerability described in CVE-2012-3749 represents a significant information disclosure flaw within Apple iOS kernel extensions APIs that directly impacts the system's security posture. This weakness exists in iOS versions prior to 6.0.1 and specifically affects how the kernel handles responses containing OSBundleMachOHeaders keys. The vulnerability stems from the kernel's improper handling of kernel memory addresses in API responses, creating an information disclosure channel that can be exploited by malicious actors. The flaw essentially exposes kernel virtual memory addresses to unprivileged applications, which violates fundamental security principles of address space layout randomization and kernel isolation.
The technical implementation of this vulnerability involves the kernel's extension APIs returning kernel memory addresses in structured responses when processing OSBundleMachOHeaders data. When an application makes an API call that triggers the kernel to include these headers in its response, the kernel inadvertently leaks memory addresses that correspond to kernel code segments and data structures. This information leakage occurs because the kernel does not properly sanitize or obfuscate memory addresses before including them in the API response, creating a pathway for attackers to gather kernel layout information. The vulnerability is particularly concerning because it directly undermines ASLR (Address Space Layout Randomization) protections, which are fundamental defenses against exploit development and code execution attacks.
The operational impact of this vulnerability extends beyond simple information disclosure, as it significantly weakens the security model of iOS devices and makes subsequent exploitation more feasible. Attackers can leverage this information to bypass ASLR mechanisms, which are designed to randomize the memory layout of processes and make it difficult for attackers to predict where kernel code resides in memory. By obtaining kernel addresses from API responses, malicious actors can craft more sophisticated exploits that target specific kernel functions or data structures, potentially leading to privilege escalation or complete system compromise. This vulnerability essentially provides attackers with a reconnaissance tool that can be used to map kernel memory layouts and identify potential targets for further exploitation. The impact is particularly severe because it affects the core security mechanisms that protect iOS devices from unauthorized access and malicious code execution.
The vulnerability aligns with CWE-200, which describes "Information Exposure," and represents a specific instance of improper information disclosure in kernel space operations. From an ATT&CK perspective, this vulnerability maps to techniques involving privilege escalation and defense evasion, as it provides attackers with information that can be used to bypass security mitigations. The flaw demonstrates poor input validation and output sanitization in kernel APIs, where memory addresses are not properly abstracted or obfuscated before being returned to user-space applications. The remediation strategy involves proper kernel memory address sanitization, ensuring that kernel addresses are not exposed in API responses, and implementing stricter access controls for kernel extension APIs. Apple addressed this vulnerability in iOS 6.0.1 through kernel updates that prevent the leakage of kernel addresses in API responses, thereby restoring proper ASLR protections and preventing attackers from using this information to compromise system security.