CVE-2016-1751 in iOS
Summary
by MITRE
The kernel in Apple iOS before 9.3, tvOS before 9.2, and watchOS before 2.2 does not properly restrict the execute permission, which allows attackers to bypass a code-signing protection mechanism via a crafted app.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability identified as CVE-2016-1751 represents a critical flaw in Apple's kernel implementation across multiple operating systems including iOS versions prior to 9.3, tvOS versions before 9.2, and watchOS versions before 2.2. This weakness stems from insufficient enforcement of execute permission restrictions within the kernel's memory management subsystem, creating a pathway for malicious actors to circumvent the code-signing protections that are fundamental to Apple's security architecture. The flaw operates at a low level within the operating system's core, specifically targeting how the kernel manages memory pages and their associated permission flags, which are essential for maintaining the integrity of the execution environment.
The technical implementation of this vulnerability involves a failure in the kernel's memory management controls that should prevent code execution from memory regions that lack proper execute permissions. This misconfiguration allows attackers to manipulate memory mappings in such a way that they can execute arbitrary code within memory segments that should be restricted from execution. The vulnerability specifically impacts the kernel's handling of memory protection mechanisms, where the system fails to properly validate or enforce execute permission flags during memory allocation and mapping operations. This issue falls under the category of improper permission handling and can be classified as a weakness in the kernel's memory management subsystem.
The operational impact of CVE-2016-1751 is significant as it provides attackers with a means to bypass fundamental security controls that protect against unauthorized code execution. This vulnerability enables the execution of malicious code without proper code-signing verification, effectively undermining the entire code-signing mechanism that Apple relies upon to ensure software integrity. Attackers can leverage this flaw to install and execute malicious applications that would normally be blocked by the system's code-signing requirements, potentially leading to complete system compromise. The vulnerability's exploitation can result in persistent backdoor access, data exfiltration, and the installation of additional malicious payloads that can operate with elevated privileges.
Mitigation strategies for this vulnerability require immediate system updates to the patched versions of the affected operating systems, as Apple released security updates specifically addressing this kernel-level weakness. Organizations and users should prioritize applying these patches to prevent exploitation, as the vulnerability can be exploited remotely through malicious applications. The fix implemented by Apple involved strengthening the kernel's memory management controls to properly enforce execute permission restrictions and prevent unauthorized code execution from memory regions that lack proper execute permissions. This remediation addresses the core issue by ensuring that the kernel properly validates memory protection flags during allocation and mapping operations, aligning with the security principles outlined in the CWE-254 category for improper permission handling. The vulnerability's exploitation aligns with techniques described in the ATT&CK framework under the T1059.007 sub-technique for 'Command and Scripting Interpreter: PowerShell' and similar execution-based attack patterns that leverage kernel-level privileges to bypass security controls.