CVE-2016-4771 in macOS
Summary
by MITRE
The kernel in Apple iOS before 10 and OS X before 10.12 allows local users to bypass intended file-access restrictions via a crafted directory pathname.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability described in CVE-2016-4771 represents a significant kernel-level privilege escalation issue affecting Apple iOS versions prior to 10.0 and OS X versions before 10.12. This flaw resides within the kernel's file access control mechanisms and allows local attackers to circumvent intended security restrictions through carefully crafted directory pathnames. The vulnerability demonstrates a critical weakness in the operating system's access control list implementation and path resolution logic, potentially enabling unauthorized file access that should otherwise be restricted to specific user contexts or system processes.
The technical nature of this vulnerability stems from improper validation of directory pathnames within the kernel's file access subsystem. Attackers can exploit this weakness by constructing malicious directory paths that bypass normal access control checks, effectively allowing them to access files and directories that would typically be protected by the system's security model. This type of flaw falls under the CWE-22 category for Path Traversal and can be classified as a privilege escalation vulnerability that operates at the kernel level. The vulnerability's exploitation typically involves crafting specific pathname sequences that confuse the kernel's path resolution algorithm, causing it to incorrectly evaluate access permissions.
The operational impact of this vulnerability extends beyond simple unauthorized file access, as it provides attackers with the ability to bypass critical security boundaries within the operating system. Local users who can execute code on the affected systems can leverage this flaw to access sensitive system files, user data, and potentially escalate their privileges to gain administrative access. This represents a serious threat to system integrity and confidentiality, particularly in environments where multiple users share the same system or where the operating system handles sensitive data. The vulnerability's presence in both iOS and OS X platforms indicates a widespread impact across Apple's ecosystem, affecting mobile and desktop environments with similar security weaknesses.
Mitigation strategies for CVE-2016-4771 primarily involve applying the official security updates released by Apple to address the kernel-level flaw. System administrators should prioritize patching affected systems to ensure that the underlying kernel vulnerabilities are resolved. Additionally, implementing proper access control policies and monitoring for unusual file access patterns can help detect potential exploitation attempts. Organizations should also consider network segmentation and privilege separation to limit the potential impact of successful exploitation. The vulnerability aligns with ATT&CK techniques related to privilege escalation and credential access, particularly the use of kernel exploits to gain elevated privileges. Regular security assessments and vulnerability scanning should include checks for this specific flaw, as well as similar path traversal vulnerabilities that could affect other system components. The remediation process should also involve comprehensive testing to ensure that the patches do not introduce compatibility issues with existing applications while maintaining the system's security posture against similar kernel-level attacks.