CVE-2012-3729 in iOS
Summary
by MITRE
The Berkeley Packet Filter (BPF) interpreter implementation in the kernel in Apple iOS before 6 accesses uninitialized memory locations, which allows local users to obtain sensitive information about the layout of kernel memory via a crafted program that uses a BPF interface.
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Analysis
by VulDB Data Team • 04/13/2021
The vulnerability identified as CVE-2012-3729 represents a critical security flaw in the Berkeley Packet Filter implementation within Apple iOS kernel components. This issue specifically affects versions of iOS prior to version 6, where the BPF interpreter fails to properly initialize memory locations during program execution. The flaw exists in the kernel-level networking subsystem that handles packet filtering operations, creating a pathway for local privilege escalation and information disclosure attacks. The BPF interpreter serves as a virtual machine for executing filtering programs, and its improper memory handling creates exploitable conditions that can reveal sensitive kernel memory structures.
The technical root cause of this vulnerability stems from uninitialized memory access patterns within the BPF interpreter's execution engine. When a malicious user crafts a specially designed BPF program and submits it through the BPF interface, the interpreter processes this program without properly initializing all memory locations that it intends to use. This uninitialized memory may contain residual data from previous operations, including kernel pointers, sensitive configuration data, or other confidential information. The vulnerability manifests as information disclosure because the BPF interpreter's memory management routines fail to clear or properly initialize memory regions before use, allowing attackers to potentially extract kernel memory layout information through carefully constructed program sequences.
The operational impact of CVE-2012-3729 extends beyond simple information disclosure, as it provides attackers with valuable insights into kernel memory organization that can be leveraged for more sophisticated attacks. Local users who can execute BPF programs on affected iOS devices gain the ability to perform memory reconnaissance, potentially mapping kernel virtual address spaces and identifying memory layout patterns. This information can be particularly valuable for attackers planning privilege escalation attacks or for bypassing kernel security mechanisms such as kernel address space layout randomization. The vulnerability aligns with CWE-457, which describes "Use of uninitialized variable," and represents a classic case of uninitialized memory access that can lead to information leakage and subsequent exploitation. From an attack framework perspective, this vulnerability could be classified under the MITRE ATT&CK technique T1059.007 for "Command and Scripting Interpreter: Unix Shell" when combined with privilege escalation techniques.
Mitigation strategies for CVE-2012-3729 primarily focus on updating to iOS version 6 or later, which contains the necessary kernel patches to address the uninitialized memory access issue. System administrators and security professionals should also implement additional monitoring of BPF program execution on affected devices, as unauthorized BPF program loading could indicate potential exploitation attempts. The vulnerability demonstrates the importance of proper memory initialization in kernel code and highlights the need for comprehensive security testing of kernel subsystems. Organizations should consider implementing least privilege principles for BPF program execution and regularly audit system configurations to prevent unauthorized access to kernel interfaces. The fix implemented by Apple likely involved ensuring proper memory initialization within the BPF interpreter before program execution, preventing access to uninitialized memory regions that could contain sensitive kernel data. This vulnerability serves as a reminder of the critical importance of memory safety in kernel implementations and the potential for seemingly minor memory management issues to create significant security risks.