CVE-2026-86900 in macOS
Summary
by MITRE • 09/15/2026
An out-of-bounds read issue was addressed with improved input validation. This issue is fixed in macOS Golden Gate 27. Mounting a maliciously crafted exFAT volume may cause unexpected system termination or kernel memory disclosure.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability described involves an out-of-bounds read condition within the file system handling logic for exFAT volumes on Apple's macOS operating systems, specifically prior to the Golden Gate 27 update. This type of flaw typically arises when a software component fails to properly verify the boundaries of memory buffers before reading data from them. In this context, the kernel or associated drivers responsible for parsing exFAT structures do not adequately validate input parameters derived from the volume's metadata or file allocation tables. When an attacker mounts a maliciously crafted exFAT volume, they can supply specially formatted headers or directory entries that contain pointers or length fields exceeding the allocated memory space. This causes the system to read data beyond the intended buffer limits, leading to undefined behavior within the kernel execution environment.
The operational impact of this vulnerability is severe due to its potential for both denial of service and information disclosure. If the out-of-bounds read accesses protected memory regions or triggers a fault in an unexpected state, it can cause the system to terminate unexpectedly, resulting in a local denial of service that affects all users on the affected machine. More critically, if the excessive read operation retrieves sensitive kernel data into user-accessible buffers or allows the attacker to inspect adjacent memory contents, it facilitates kernel memory disclosure. This leakage can expose cryptographic keys, process identifiers, stack pointers, and other critical security artifacts that attackers can leverage for further exploitation, such as privilege escalation attacks against higher-privileged processes running on the system.
From a classification perspective, this issue aligns with CWE-125, which defines out-of-bounds read vulnerabilities where software reads data past the end or before the beginning of the intended buffer. The attack vector is classified under ATT&CK technique T1083, specifically related to file and directory discovery, as it requires physical access or the ability to mount external storage media. This highlights the risk associated with removable media in environments where users frequently connect unknown drives to their workstations. The vulnerability underscores the importance of robust input validation mechanisms within kernel-level drivers that handle complex file system formats like exFAT, which are commonly used for cross-platform data exchange but often contain intricate structures susceptible to malformed inputs.
Mitigation strategies primarily involve applying the official software update provided by Apple in macOS Golden Gate 27, which addresses the root cause through improved input validation logic within the affected drivers. Administrators should ensure that all systems running vulnerable versions of macOS are patched promptly to close this security gap. Additionally, organizations can implement defensive measures such as restricting the automatic mounting of external volumes or requiring user confirmation before mounting removable media to reduce the attack surface. Security awareness training for users regarding the risks of connecting unknown storage devices is also recommended to complement technical controls and prevent exploitation through social engineering tactics that might lead a user to mount maliciously crafted exFAT drives.