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. The flaw is categorized under [CWE-362] (Concurrent Execution using Shared Resource with Improper Synchronization). Apple addressed the issue by adding additional validation in macOS Sequoia 15.7.5, macOS Sonoma 14.8.5, and macOS Tahoe 26.4. A successful exploit grants the attacker access to resources outside the sandbox confinement, undermining a core macOS security boundary.

Critical Impact

An application running within the macOS sandbox can exploit timing-dependent behavior to break containment and access system resources with broader privileges than intended.

Affected Products

• Apple macOS Sequoia (prior to 15.7.5)
• Apple macOS Sonoma (prior to 14.8.5)
• Apple macOS Tahoe (prior to 26.4)

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

The vulnerability is a race condition in a macOS component used to enforce sandbox boundaries. Apple's advisories describe the fix as "additional validation," indicating that the original code path lacked sufficient state verification between concurrent operations. An attacker-controlled app can interleave operations in a way that causes the system to act on a value or resource state that has changed after an initial check.

The attack vector is local and requires no privileges or user interaction, but the attack complexity is high because the attacker must reliably win a timing window. Successful exploitation produces a scope change, with high impact to confidentiality, integrity, and availability across the affected system. Sandbox escape on macOS commonly serves as a chained step in broader exploit chains targeting full system compromise.

Root Cause

The root cause is improper synchronization between concurrent operations that share state used in sandbox enforcement. Without atomic validation, a Time-of-Check to Time-of-Use (TOCTOU) condition arises. The vendor patch introduces validation that closes the window between the security check and the action being authorized.

Attack Vector

A locally installed application running inside the sandbox triggers concurrent operations to manipulate shared state. By repeatedly racing a privileged operation against a state-modifying call, the app causes the sandbox enforcement logic to make a decision based on stale or attacker-controlled data. The result is execution or resource access outside the sandbox profile.

No verified exploit code is publicly available. See the Apple Support Advisory #126794, Apple Support Advisory #126795, and Apple Support Advisory #126796 for vendor-supplied technical details.

Detection Methods for CVE-2026-28891

Indicators of Compromise

• Sandboxed processes spawning child processes or accessing file paths outside their declared sandbox container.
• Unexpected access to user data directories, keychain files, or system configuration paths from App Store or third-party sandboxed apps.
• Repeated, rapid invocations of the same system call from a single sandboxed process, consistent with a race-window brute force.

Detection Strategies

• Monitor sandboxd and kernel log entries for sandbox violation events generated by user applications.
• Audit EndpointSecurity framework events for ES_EVENT_TYPE_NOTIFY_EXEC and file open events that cross expected sandbox boundaries.
• Baseline normal syscall patterns for sandboxed apps and alert on statistical anomalies indicative of race-condition exploitation.

Monitoring Recommendations

• Forward macOS Unified Log entries from the com.apple.sandbox and com.apple.kernel subsystems to a centralized log platform.
• Track installed macOS build numbers across the fleet and flag endpoints not patched to 15.7.5, 14.8.5, or 26.4.
• Alert on first-seen process lineage where a sandboxed application is the parent of unexpected privileged operations.

How to Mitigate CVE-2026-28891

Immediate Actions Required

• Update affected endpoints to macOS Sequoia 15.7.5, macOS Sonoma 14.8.5, or macOS Tahoe 26.4 as applicable.
• Inventory installed third-party applications and restrict execution of untrusted apps until patches are deployed.
• Verify managed software update policies are enforcing the patched build through your MDM solution.

Patch Information

Apple released fixes in macOS Sequoia 15.7.5, macOS Sonoma 14.8.5, and macOS Tahoe 26.4. Refer to Apple Support Advisory #126794, Apple Support Advisory #126795, and Apple Support Advisory #126796 for build-specific details and the full list of addressed CVEs.

Workarounds

• No vendor-supplied workaround exists; patching is the only supported remediation.
• Restrict installation of untrusted applications via MDM application allowlisting until updates are applied.
• Enforce Gatekeeper and notarization requirements to reduce exposure to unsigned or unverified apps.

# Verify macOS build version on managed endpoints
sw_vers -productVersion
softwareupdate --list
sudo softwareupdate -i -a -R