CVE-2026-28891: Apple macOS Race Condition Vulnerability

CVE-2026-28891 Overview

CVE-2026-28891 is a race condition vulnerability in Apple macOS that allows a malicious application to escape its sandbox environment. The vulnerability arises from insufficient validation during concurrent operations, enabling attackers to exploit timing windows to bypass security boundaries. Apple addressed this flaw with additional validation logic in the affected components.

Critical Impact

A malicious application can break out of its sandbox, potentially gaining access to sensitive user data, system resources, and other applications' data that would normally be protected by macOS's sandboxing security model.

Affected Products

• macOS Tahoe versions prior to 26.4
• macOS Sequoia versions prior to 15.7.5
• macOS Sonoma versions prior to 14.8.5

Discovery Timeline

• 2026-03-25 - CVE-2026-28891 published to NVD
• 2026-03-25 - Last updated in NVD database

Technical Details for CVE-2026-28891

Vulnerability Analysis

This vulnerability is classified as CWE-362 (Race Condition), a concurrency flaw where the behavior of the system depends on the sequence or timing of uncontrollable events. In the context of macOS, the sandbox is a critical security mechanism that restricts an application's ability to access system resources, files, and other applications' data beyond what is explicitly permitted.

The race condition in CVE-2026-28891 occurs when concurrent operations are not properly synchronized, creating a window of opportunity where an attacker can manipulate state between a security check and the subsequent use of that state. This Time-of-Check to Time-of-Use (TOCTOU) pattern allows a sandboxed application to perform actions that should be restricted by the sandbox policy.

The vulnerability requires local access to exploit, meaning an attacker would need to execute a malicious application on the target system. However, once exploitation is successful, the impact is severe—complete escape from the sandbox could allow the attacker to access confidential user data, execute privileged operations, and potentially compromise other applications on the system.

Root Cause

The root cause of CVE-2026-28891 is inadequate synchronization and validation during concurrent operations within macOS's sandbox enforcement mechanisms. The vulnerability exists because the system performs security validation checks that can be bypassed when specific timing conditions are met. Apple's fix introduces additional validation to eliminate the race window that allowed the sandbox escape.

Attack Vector

The attack requires local execution of a malicious application on the target macOS system. An attacker could distribute the malicious application through various means, including:

• Tricking users into downloading and running untrusted applications
• Exploiting supply chain vulnerabilities to inject malicious code into legitimate applications
• Using social engineering to convince users to bypass Gatekeeper protections

Once the malicious application is running within the sandbox, it can exploit the race condition to escape confinement and gain access to protected resources. The attack does not require any user interaction beyond initial application execution, and no special privileges are needed to exploit the vulnerability.

Detection Methods for CVE-2026-28891

Indicators of Compromise

• Unusual process behavior where sandboxed applications access resources outside their permitted scope
• Unexpected file system access attempts by applications that should be restricted by sandbox policies
• Anomalous IPC (Inter-Process Communication) patterns indicating sandbox boundary violations
• Applications spawning child processes with elevated or unrestricted sandbox profiles

Detection Strategies

• Monitor system logs for sandbox violation attempts and unusual access patterns from sandboxed applications
• Deploy endpoint detection solutions capable of identifying race condition exploitation attempts
• Implement behavioral analysis to detect applications accessing resources inconsistent with their sandbox entitlements
• Use SentinelOne's real-time monitoring capabilities to identify suspicious process behaviors indicative of sandbox escape attempts

Monitoring Recommendations

• Enable comprehensive logging of sandbox-related events in the macOS Unified Logging system
• Configure alerts for applications that exhibit behavior inconsistent with their declared entitlements
• Monitor for applications making rapid, repeated access attempts that could indicate exploitation of race conditions
• Implement file integrity monitoring on sensitive system directories that should be protected from sandboxed applications

How to Mitigate CVE-2026-28891

Immediate Actions Required

• Update all affected macOS systems to the patched versions immediately: macOS Tahoe 26.4, macOS Sequoia 15.7.5, or macOS Sonoma 14.8.5
• Review installed applications and remove any untrusted or unnecessary software
• Ensure Gatekeeper and System Integrity Protection (SIP) are enabled on all systems
• Implement application allowlisting where possible to prevent execution of unauthorized applications

Patch Information

Apple has released security updates addressing CVE-2026-28891 with additional validation to eliminate the race condition. Detailed patch information is available in the following Apple Security Advisories:

• Apple Support Document #126794 - macOS Tahoe 26.4 Security Update
• Apple Support Document #126795 - macOS Sequoia 15.7.5 Security Update
• Apple Support Document #126796 - macOS Sonoma 14.8.5 Security Update

Organizations should prioritize deployment of these updates through their patch management systems.

Workarounds

• Restrict application installation to only trusted sources and enterprise-approved applications
• Enable strict Gatekeeper settings to prevent execution of applications from unidentified developers
• Implement network segmentation to limit the impact of potential sandbox escapes
• Use mobile device management (MDM) solutions to enforce security policies and restrict application installations on managed macOS devices

# Verify Gatekeeper status and enforce strictest settings
spctl --status
sudo spctl --master-enable

# Verify System Integrity Protection is enabled
csrutil status

# Check macOS version to confirm patched version is installed
sw_vers -productVersion