CVE-2016-1756 in iOS
Summary
by MITRE
The kernel in Apple iOS before 9.3 and OS X before 10.11.4 allows attackers to execute arbitrary code in a privileged context or cause a denial of service (NULL pointer dereference) via a crafted app.
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Analysis
by VulDB Data Team • 11/11/2024
The vulnerability identified as CVE-2016-1756 represents a critical kernel-level flaw affecting Apple iOS versions prior to 9.3 and OS X versions prior to 10.11.4. This issue stems from a NULL pointer dereference condition that occurs within the kernel's memory management subsystem, creating a potential pathway for attackers to escalate privileges or disrupt system operations. The vulnerability exists in the kernel's handling of memory references, specifically when processing crafted applications that manipulate kernel memory structures in unexpected ways.
The technical exploitation of this vulnerability involves an attacker crafting a malicious application that triggers a NULL pointer dereference within the kernel execution context. When the kernel attempts to access memory at a NULL address, the system either crashes with a segmentation fault or potentially allows the malicious code to execute with elevated privileges. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions in software systems. The kernel's failure to properly validate memory references creates a dangerous condition where untrusted input from a crafted application can directly influence kernel execution flow.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to encompass potential privilege escalation attacks. An attacker who successfully exploits this vulnerability could execute arbitrary code with kernel-level privileges, effectively bypassing all user-space security controls and gaining complete system control. This represents a severe compromise of the operating system's security model, as the kernel serves as the fundamental protection layer for all system resources. The vulnerability's potential for privilege escalation aligns with ATT&CK technique T1068 which describes the exploitation of legitimate credentials and system access to gain elevated privileges.
The exploitation scenario typically involves an attacker distributing a malicious application through legitimate app stores or through targeted delivery methods. Once installed, the application triggers the kernel vulnerability through specific memory access patterns that cause the NULL pointer dereference. The system response may manifest as an immediate crash and reboot, or in more sophisticated cases, the vulnerability could be leveraged to establish persistent backdoors or execute stealthy code execution. This vulnerability demonstrates the critical importance of kernel security validation and proper input sanitization, as even a single NULL pointer dereference can compromise entire operating system security models.
Mitigation strategies for CVE-2016-1756 primarily focus on applying the official security patches released by Apple for iOS 9.3 and OS X 10.11.4. System administrators should prioritize immediate deployment of these updates across all affected devices to prevent exploitation. Additionally, organizations should implement application whitelisting policies to prevent installation of untrusted applications, particularly those that might trigger kernel-level vulnerabilities. The vulnerability highlights the necessity of maintaining current security patches and implementing robust application security controls. Network monitoring should also be enhanced to detect anomalous behavior that might indicate exploitation attempts, while endpoint protection solutions should be configured to block potentially malicious applications before they can execute and trigger kernel-level vulnerabilities.