CVE-2026-84516: Apple macOS Use-After-Free Vulnerability

CVE-2026-84516 Overview

CVE-2026-84516 is an out-of-bounds read vulnerability [CWE-125] affecting multiple versions of Apple macOS. Processing a maliciously crafted file may result in unexpected app termination or disclosure of process memory. Apple addressed the issue through improved bounds checking in macOS Golden Gate 27, macOS Sequoia 15.8, and macOS Tahoe 26.7.

The vulnerability requires user interaction to trigger, typically through opening a specially crafted file. Successful exploitation can leak sensitive information from process memory or crash the affected application.

Critical Impact
Attackers can leverage a malicious file to read out-of-bounds memory, disclosing process memory contents or terminating the target application.

Affected Products

Apple macOS versions prior to Golden Gate 27
Apple macOS versions prior to Sequoia 15.8
Apple macOS versions prior to Tahoe 26.7

Discovery Timeline

2026-09-14 - CVE-2026-84516 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-84516

Vulnerability Analysis

The vulnerability is classified as an out-of-bounds read [CWE-125]. When the affected macOS component parses a maliciously crafted file, it reads memory beyond the intended buffer boundaries. This behavior can expose adjacent memory contents to the attacker or cause the processing application to terminate unexpectedly.

Apple's advisories confirm the fix relies on improved bounds checking within the affected file parsing logic. The issue impacts macOS Golden Gate, macOS Sequoia, and macOS Tahoe release branches. Apple has not publicly disclosed the specific system component or file format involved.

Root Cause

The root cause is missing or insufficient validation of buffer boundaries during file processing. When parsing an attacker-controlled file, the affected code path calculates or trusts a length or offset value that references memory outside the allocated buffer. The resulting read operation returns unintended data or triggers a memory access violation.

Attack Vector

Exploitation requires the victim to process a maliciously crafted file with an affected macOS component. Delivery vectors include email attachments, downloaded files, or files served through web content. The CVSS vector indicates network-based delivery with required user interaction. Successful exploitation impacts confidentiality through memory disclosure and availability through application termination.

No public proof-of-concept exploit is currently available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the Apple Support Document #149035, Apple Support Document #149042, and Apple Support Document #149043 for vendor-specific technical detail.

Detection Methods for CVE-2026-84516

Indicators of Compromise

Unexpected termination or crash reports from macOS applications processing untrusted files.
Crash logs in ~/Library/Logs/DiagnosticReports/ referencing segmentation faults or memory access violations during file parsing.
Delivery of unusual or malformed files through email, messaging, or web downloads to macOS endpoints.

Detection Strategies

Monitor endpoint telemetry for repeated application crashes associated with specific file types or parsers.
Correlate file download events with subsequent process crashes on the same host.
Track macOS build versions across the fleet to identify systems running vulnerable releases prior to 15.8, 26.7, or Golden Gate 27.

Monitoring Recommendations

Ingest macOS Unified Logs and crash reports into a centralized logging platform for correlation.
Alert on anomalous file delivery patterns targeting macOS users, including uncommon file extensions or MIME types.
Maintain an asset inventory that tracks OS build versions to prioritize patch deployment.

How to Mitigate CVE-2026-84516

Immediate Actions Required

Update all macOS endpoints to macOS Golden Gate 27, macOS Sequoia 15.8, or macOS Tahoe 26.7 as applicable.
Prioritize patching for users who routinely handle untrusted files from external sources.
Communicate user awareness guidance to avoid opening unexpected files from unknown senders.

Patch Information

Apple has released fixes in macOS Golden Gate 27, macOS Sequoia 15.8, and macOS Tahoe 26.7. Consult the Apple Support Document #149035, Apple Support Document #149042, and Apple Support Document #149043 for version-specific update instructions.

Workarounds

Restrict handling of untrusted files on unpatched macOS systems until updates are applied.
Use email and web gateway controls to filter or sandbox potentially malicious file attachments.
Enforce least-privilege configurations to limit the impact of memory disclosure on affected applications.

bash

# Verify macOS version and apply available updates
sw_vers -productVersion
sudo softwareupdate --install --all --restart