CVE-2026-86991 in iOS
Summary
by MITRE • 10/26/2026
A buffer overflow was addressed with improved bounds checking. This issue is fixed in iOS 26.7.2 and iPadOS 26.7.2, iOS 27.2 and iPadOS 27.2, macOS Golden Gate 27.2, macOS Sequoia 15.8.2, macOS Tahoe 26.7.2, visionOS 27.2. Processing a maliciously crafted file may lead to unexpected process termination.
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Analysis
by VulDB Data Team • 10/26/2026
The vulnerability described involves a buffer overflow condition within the operating system's file processing subsystems across multiple Apple platforms including iOS, iPadOS, macOS, and visionOS. A buffer overflow occurs when a program writes more data to a fixed-length block of memory than it can hold, causing adjacent memory locations to be overwritten with potentially malicious or corrupted data. In this specific instance, the flaw was addressed by implementing improved bounds checking mechanisms within the code responsible for parsing and handling incoming files. Bounds checking is a critical security control that ensures an application only accesses memory regions it has been explicitly authorized to use, thereby preventing out-of-bounds reads and writes that can lead to arbitrary code execution or system instability.
The operational impact of this vulnerability centers on the potential for unexpected process termination when processing maliciously crafted files. While buffer overflows are frequently associated with remote code execution vulnerabilities where an attacker gains control over the target machine, in this case, the primary consequence identified is denial of service through application crashes. When a specially constructed file triggers the overflow, it corrupts the memory state of the executing process, leading to immediate termination by the operating system's crash handlers or signal processors. This disruption affects availability and can be exploited for simple denial-of-service attacks against services that automatically parse user-supplied files without sufficient validation.
From a classification perspective, this vulnerability aligns with CWE-120 Buffer Copy without Checking Size of Input Classic buffer overflow and potentially CWE-787 Out-of-bounds Write if the overwrite affects critical control structures such as return addresses or function pointers. Although the immediate impact is process termination, the underlying mechanism remains dangerous because improper memory handling can often be leveraged for more severe exploits depending on the specific context in which the vulnerable code executes. The ATT&CK framework would categorize this under techniques related to resource hijacking or denial of service, specifically focusing on how attackers might exploit software flaws to disrupt normal operations without necessarily achieving persistence or privilege escalation immediately.
Mitigation strategies primarily involve applying the provided vendor patches as soon as possible. For end-users and administrators, updating iOS to version 26.7.2 or 27.2, iPadOS to corresponding versions, macOS Sequoia to 15.8.2, macOS Tahoe to 26.7.2, macOS Golden Gate to 27.2, and visionOS to 27.2 is essential to resolve the underlying memory management flaw. Additionally, organizations should enforce strict input validation policies for any custom applications that process external files, ensuring that file sizes are checked against expected limits before processing begins. Implementing defense-in-depth measures such as address space layout randomization and data execution prevention further reduces the likelihood of successful exploitation even if similar vulnerabilities exist in unpatched components.