CVE-2024-40849: macOS Sequoia Sandbox Escape Vulnerability

CVE-2024-40849 Overview

CVE-2024-40849 is a race condition vulnerability affecting macOS Sequoia that allows an application to break out of its sandbox environment. The vulnerability stems from insufficient validation during time-sensitive operations, creating a window where an attacker-controlled application can escape sandbox restrictions and potentially access protected system resources or user data.

Critical Impact

A malicious application can exploit this race condition to escape sandbox containment, potentially gaining unauthorized access to system resources, sensitive user data, and other sandboxed applications' data on affected macOS systems.

Affected Products

• macOS Sequoia versions prior to 15.1
• Applications running in sandboxed environments on vulnerable macOS versions

Discovery Timeline

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

Technical Details for CVE-2024-40849

Vulnerability Analysis

This vulnerability is classified as CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization), commonly known as a race condition. The flaw exists in macOS's sandbox enforcement mechanism, where timing-dependent operations lack proper synchronization and validation controls.

When an application attempts to access protected resources, macOS's sandbox framework performs security checks to validate the request against the application's entitlements and sandbox profile. However, a race condition exists where the state being checked can be modified between the time of the security check and the actual resource access operation. This Time-of-Check Time-of-Use (TOCTOU) pattern allows a malicious application to manipulate system state during this vulnerable window.

The sandbox escape capability is particularly concerning because macOS sandboxing is a fundamental security boundary designed to contain application behavior and protect user data from potentially malicious software.

Root Cause

The root cause is a race condition (CWE-362) in macOS's sandbox validation logic. The vulnerability occurs due to insufficient atomic operations or locking mechanisms during security-critical state transitions. When the sandbox framework validates an application's permissions, there is a timing window where concurrent operations can interfere with or bypass the validation checks.

The absence of proper synchronization primitives means that rapid, concurrent requests from a malicious application can exploit the gap between permission checks and resource access, effectively allowing operations that should be denied by the sandbox policy.

Attack Vector

The attack leverages the network-accessible attack vector with low complexity, requiring no privileges or user interaction. In practice, exploitation would involve:

1. Timing Manipulation: A malicious application deliberately triggers rapid, concurrent operations designed to hit the vulnerable timing window in sandbox validation
2. State Race: The application races between the security check and the protected operation, attempting to modify the checked state before access is granted
3. Sandbox Escape: Upon successful exploitation, the application gains access to resources outside its sandbox container

The exploitation requires precise timing and may need multiple attempts to successfully hit the race window. However, the lack of required privileges or user interaction makes this a significant risk for systems running untrusted applications.

Detection Methods for CVE-2024-40849

Indicators of Compromise

• Unusual sandbox violation logs in the macOS Unified Logging system showing applications attempting rapid, repeated access to protected resources
• Applications exhibiting abnormal file system access patterns, particularly accessing directories outside their sandbox container
• Elevated system call activity related to sandbox operations, especially around resource access validation
• Anomalous process behavior where sandboxed applications access other applications' data or system resources

Detection Strategies

• Monitor macOS sandbox violation logs using log stream --predicate 'subsystem == "com.apple.sandbox"' for unusual patterns
• Implement endpoint detection rules to identify applications making rapid sequential attempts to access protected resources
• Use SentinelOne's behavioral AI to detect applications exhibiting sandbox escape behaviors or accessing resources inconsistent with their entitlements
• Deploy file integrity monitoring on sensitive directories to detect unauthorized access from sandboxed applications

Monitoring Recommendations

• Enable detailed sandbox logging on critical macOS endpoints to capture potential exploitation attempts
• Configure alerting for applications that suddenly access resources outside their expected sandbox scope
• Monitor for process chains where sandboxed applications spawn unexpected child processes with elevated capabilities
• Review application entitlements regularly and audit any applications requesting unusual sandbox exceptions

How to Mitigate CVE-2024-40849

Immediate Actions Required

• Update macOS to Sequoia version 15.1 or later immediately on all affected systems
• Review and audit installed applications, removing any untrusted or unnecessary software that could potentially exploit this vulnerability
• Enable additional logging on critical systems to detect potential exploitation attempts during the patching window
• Consider restricting application installations to only App Store or MDM-managed applications until patching is complete

Patch Information

Apple has addressed this vulnerability in macOS Sequoia 15.1 with additional validation to eliminate the race condition. The patch implements proper synchronization and atomic operations in the sandbox validation path to prevent TOCTOU exploitation.

For detailed patch information, refer to the Apple Support Article.

System administrators should prioritize deployment of macOS Sequoia 15.1 through their existing software update mechanisms, whether through Apple Business Manager, MDM solutions, or direct system updates.

Workarounds

• Restrict execution of untrusted applications using macOS Gatekeeper and application allowlisting policies
• Implement network segmentation to limit the potential impact if a sandbox escape occurs on an endpoint
• Use SentinelOne's application control features to prevent unauthorized applications from running
• Enable stricter sandbox profiles for applications where custom configurations are possible, though this may impact application functionality