CVE-2016-4776 in tvOS
Summary
by MITRE
The kernel in Apple iOS before 10, OS X before 10.12, tvOS before 10, and watchOS before 3 allows attackers to obtain sensitive memory-layout information or cause a denial of service (out-of-bounds read) via a crafted app, a different vulnerability than CVE-2016-4773 and CVE-2016-4774.
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Analysis
by VulDB Data Team • 09/21/2022
The vulnerability identified as CVE-2016-4776 represents a critical information disclosure and denial of service flaw within Apple's kernel implementations across multiple operating systems. This vulnerability affects iOS versions prior to 10.0, OS X versions prior to 10.12, tvOS versions prior to 10.0, and watchOS versions prior to 3.0, exposing millions of devices to potential exploitation. The flaw manifests through improper memory handling within kernel space, specifically allowing attackers to craft malicious applications that can trigger out-of-bounds read operations. Such vulnerabilities are particularly dangerous because they operate at the kernel level where privileges are highest, potentially enabling attackers to extract sensitive memory layout information that could be used for more sophisticated attacks.
The technical implementation of this vulnerability stems from inadequate bounds checking within kernel memory management routines. When a crafted application is executed, it can manipulate kernel data structures in ways that cause the system to read memory locations beyond their allocated boundaries. This out-of-bounds read behavior enables attackers to access memory contents that should remain protected, potentially revealing kernel memory layout information such as address space layout randomization (ASLR) values, kernel function pointers, or other sensitive data structures. The vulnerability operates at the intersection of multiple attack vectors as defined by the ATT&CK framework, specifically involving privilege escalation and credential access techniques that leverage kernel-level flaws.
The operational impact of CVE-2016-4776 extends beyond simple information disclosure, as the out-of-bounds read conditions can also trigger system instability leading to denial of service scenarios. Attackers can leverage this vulnerability to either extract sensitive kernel memory information for use in subsequent attacks or to crash system processes, effectively creating a denial of service condition that disrupts normal device operation. The vulnerability's relationship to CVE-2016-4773 and CVE-2016-4774 demonstrates a pattern of similar kernel-level flaws within Apple's operating systems during this period, indicating potential systemic issues in memory management implementations. From a cybersecurity perspective, this vulnerability aligns with CWE-129, which describes improper validation of array indices, and represents a classic example of how kernel-level memory corruption can lead to both information disclosure and system instability.
Mitigation strategies for CVE-2016-4776 require immediate system updates to the patched versions of affected operating systems, as Apple released security updates addressing this specific kernel vulnerability. Organizations should implement comprehensive patch management procedures to ensure all affected devices receive the necessary updates promptly. Additionally, security monitoring should focus on detecting anomalous application behavior that might indicate exploitation attempts, particularly around kernel memory access patterns. The vulnerability highlights the importance of maintaining current system patches and implementing robust security controls that limit the attack surface for kernel-level exploits. Network administrators should consider implementing application whitelisting policies to prevent the execution of untrusted applications that could potentially exploit this vulnerability, while also monitoring for indicators of compromise related to kernel memory access anomalies.