CVE-2026-84523 in iOS
Summary
by MITRE • 09/15/2026
An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in iOS 26.7 and iPadOS 26.7, iOS 27 and iPadOS 27, macOS Golden Gate 27, macOS Sequoia 15.8, macOS Tahoe 26.7, tvOS 27, visionOS 27, watchOS 27. An app may be able to cause unexpected system termination or write kernel memory.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 09/15/2026
The vulnerability described constitutes a critical out-of-bounds write flaw within the core operating systems of Apple devices, specifically affecting iOS, iPadOS, macOS, tvOS, visionOS, and watchOS versions prior to those listed in the patch notes. This type of memory corruption error occurs when software writes data beyond the boundaries of allocated memory buffers, potentially overwriting adjacent memory structures that are critical for system stability or security enforcement mechanisms. The root cause lies in insufficient validation of input parameters during processing operations, allowing an application to manipulate pointer arithmetic or buffer indices such that they reference unauthorized regions of kernel space rather than their intended destination within user-space allocations.
From a technical perspective, this flaw aligns with Common Weakness Enumeration identifier CWE-787, which defines out-of-bounds write vulnerabilities as conditions where software writes data past the end or before the beginning of the intended buffer. In the context of modern operating systems like iOS and macOS, such errors are particularly dangerous because they can bridge the boundary between user space and kernel space. When an application triggers this condition, it may corrupt critical kernel data structures, leading to unpredictable system behavior ranging from minor glitches to complete catastrophic failure. The presence of improved bounds checking in the fixed versions indicates that Apple has implemented stricter validation logic to ensure that memory access requests remain within legally allocated boundaries, thereby preventing unauthorized writes.
The operational impact of this vulnerability is severe due to its potential for privilege escalation and denial of service. An attacker who can execute arbitrary code or manipulate specific inputs within a vulnerable application could exploit the out-of-bounds write to overwrite kernel memory with malicious payloads. This capability allows for arbitrary code execution at ring 0, effectively granting full control over the device's operating system. Furthermore, even without successful exploitation for remote code execution, the instability caused by corrupting kernel memory can lead to unexpected system termination or crashes, resulting in a denial of service condition that disrupts normal user operations and compromises availability.
This vulnerability maps directly to several tactics within the MITRE ATT&CK framework, particularly those related to privilege escalation and defense evasion. The ability to write to arbitrary kernel memory facilitates techniques associated with T1068 Exploitation for Privilege Escalation, as it allows lower-privileged processes to gain higher-level access rights. Additionally, by modifying kernel structures, an attacker might attempt to hide their presence or disable security monitoring tools, aligning with defense evasion tactics such as T1562 Impair Defenses. The exploitation of memory corruption bugs like this one is a common vector for advanced persistent threats seeking long-term access to high-value targets on mobile and desktop platforms.
Mitigation strategies primarily rely on the deployment of the software updates provided by Apple, which include iOS 26.7, iPadOS 26.7, iOS 27, iPadOS 27, macOS Golden Gate 27, macOS Sequoia 15.8, macOS Tahoe 26.7, tvOS 27, visionOS 27, and watchOS 27. Organizations should prioritize patching these endpoints to eliminate the underlying memory corruption flaw. In addition to timely updates, implementing strict application sandboxing policies can limit the potential blast radius if an exploit is attempted by restricting the permissions granted to individual applications. Security teams should also monitor for anomalous system behavior or unexpected terminations that might indicate exploitation attempts in environments where patching has not yet been fully implemented.