CVE-2024-40849: Apple macOS Race Condition Vulnerability

CVE-2024-40849 Overview

CVE-2024-40849 is a race condition vulnerability in Apple macOS that allows a malicious application to escape its sandbox. Apple addressed the issue with additional validation in macOS Sequoia 15.1. The flaw is categorized under [CWE-362], concurrent execution using shared resource with improper synchronization.

A successful exploit lets an app bypass the macOS App Sandbox, which is designed to constrain application access to system resources and user data. Apple has not reported in-the-wild exploitation, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Critical Impact

A sandboxed application can break containment and access resources outside its sandbox boundary on unpatched macOS systems.

Affected Products

• Apple macOS versions prior to macOS Sequoia 15.1
• Applications relying on the macOS App Sandbox for isolation
• Systems running affected macOS releases on supported Apple hardware

Discovery Timeline

• 2026-04-02 - CVE-2024-40849 published to NVD
• 2026-04-03 - Last updated in NVD database

Technical Details for CVE-2024-40849

Vulnerability Analysis

The vulnerability is a race condition in macOS that affects sandbox enforcement. Race conditions occur when the behavior of code depends on the relative timing of two or more operations that access shared state without sufficient synchronization. In this case, an attacker controlling a sandboxed process can exploit the timing window to perform actions that the sandbox policy would otherwise block.

Apple's advisory describes the fix as "additional validation," indicating that the original code path performed a check that could be invalidated before the protected operation completed. The vulnerability is classified under [CWE-362]. Apple has not published exploitation details and no public proof-of-concept is available.

Root Cause

The root cause is insufficient validation between the time a sandbox policy decision is made and the time the protected operation is performed. This pattern is commonly referred to as a Time-of-Check Time-of-Use (TOCTOU) flaw. The patched code adds validation that closes the timing window, ensuring that the conditions evaluated at policy check time still hold when the operation executes.

Attack Vector

An attacker must first achieve code execution inside a sandboxed application, typically by delivering a malicious app, plugin, or document handler. The malicious code then triggers the race condition to perform a sandbox-restricted action. Successful exploitation lets the attacker access files, IPC endpoints, or APIs that the sandbox profile would otherwise deny, enabling further compromise of user data.

No verified proof-of-concept code has been published. Technical details are limited to Apple's advisory at Apple Support Article 121564.

Detection Methods for CVE-2024-40849

Indicators of Compromise

• Sandboxed processes accessing file paths or system resources outside their declared sandbox container
• Unexpected child processes spawned by applications that should be confined by the App Sandbox
• Anomalous Mach IPC or XPC connections originating from sandboxed apps to privileged services

Detection Strategies

• Monitor sandboxd and Endpoint Security framework events for sandbox violations and policy decisions that precede unexpected resource access.
• Baseline normal behavior for sandboxed applications and alert on deviations such as filesystem writes outside container directories.
• Correlate process telemetry with file access events to identify TOCTOU-style patterns where checks and uses target the same resource in rapid succession.

Monitoring Recommendations

• Ingest macOS Unified Logs and Endpoint Security telemetry into a centralized analytics platform for retrospective hunting.
• Track installed macOS build numbers across the fleet and flag endpoints running versions earlier than macOS Sequoia 15.1.
• Alert on installation of unsigned or untrusted applications, which are the most likely delivery vehicle for sandbox escape exploits.

How to Mitigate CVE-2024-40849

Immediate Actions Required

• Update affected macOS endpoints to macOS Sequoia 15.1 or later using Software Update or your mobile device management platform.
• Inventory the fleet to identify systems running pre-15.1 builds and prioritize patch deployment.
• Restrict installation of applications to those signed by trusted developers and distributed through vetted channels.

Patch Information

Apple resolved CVE-2024-40849 in macOS Sequoia 15.1 by adding validation that eliminates the race condition. Refer to the Apple Support Article for the official advisory and the complete list of fixes included in this release. No backports for earlier macOS major versions are referenced in the advisory.

Workarounds

• No vendor-supplied workaround exists; applying the macOS Sequoia 15.1 update is the supported remediation.
• Enforce Gatekeeper and notarization requirements to reduce the likelihood of running untrusted sandboxed code.
• Apply application allowlisting through MDM configuration profiles to block execution of unapproved software until patching is complete.

# Verify the installed macOS version meets the patched build
sw_vers -productVersion

# Trigger an MDM-managed software update check
sudo softwareupdate --list
sudo softwareupdate --install --all --restart