CVE-2026-28817: Apple macOS Race Condition Vulnerability

CVE-2026-28817 Overview

CVE-2026-28817 is a race condition vulnerability in Apple macOS that allows a sandboxed process to circumvent sandbox restrictions. Apple addressed the issue with improved state handling across multiple macOS versions. The flaw is classified under [CWE-362] (Concurrent Execution using Shared Resource with Improper Synchronization).

The vulnerability affects macOS Sequoia, macOS Sonoma, and macOS Tahoe. Successful exploitation enables a process confined by the App Sandbox to escape its container and access resources outside its assigned profile. Apple released patches in macOS Sequoia 15.7.5, macOS Sonoma 14.8.5, and macOS Tahoe 26.4.

Critical Impact

A sandboxed process can bypass sandbox restrictions through a race condition, breaking a core macOS security boundary used to contain untrusted code.

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-2026-28817 published to NVD
• 2026-03-25 - Last updated in NVD database

Technical Details for CVE-2026-28817

Vulnerability Analysis

The vulnerability is a race condition affecting macOS sandbox state management. The App Sandbox enforces fine-grained policies that restrict file access, network operations, and inter-process communication for confined processes. When state transitions inside the sandbox enforcement path are not properly synchronized, a process can manipulate timing to act on stale or inconsistent state.

An attacker with the ability to run code inside a sandboxed process can race the sandbox's state checks. By winning the race, the attacker performs operations that the sandbox profile would otherwise deny. Apple addressed the issue with improved state handling, indicating that the fix tightens synchronization around the affected check-and-act sequences.

The attack requires local code execution and high attack complexity, but no privileges or user interaction. The scope is changed, reflecting that a successful escape impacts resources beyond the originally constrained sandbox boundary.

Root Cause

The root cause is improper synchronization between sandbox policy checks and the operations they protect. This is a classic time-of-check to time-of-use (TOCTOU) pattern characteristic of [CWE-362] defects, where shared state can change between validation and use.

Attack Vector

Exploitation requires local code execution inside a sandboxed process, such as a browser renderer, a Mac App Store application, or a sandboxed helper. The attacker triggers concurrent operations that race the sandbox's state transitions. No verified public exploit or proof-of-concept is available for CVE-2026-28817.

The vulnerability is typically chained with an initial code execution primitive, for example a memory corruption bug in a sandboxed application, to escalate from in-sandbox execution to broader system access.

Detection Methods for CVE-2026-28817

Indicators of Compromise

• Sandboxed processes spawning child processes or accessing file paths outside their declared sandbox container.
• Unexpected sandbox_check denials followed by successful access to the same resource within a short interval.
• Anomalous xpc or Mach message traffic originating from processes that normally communicate only with their parent application.

Detection Strategies

• Monitor Endpoint Security framework events (ES_EVENT_TYPE_NOTIFY_EXEC, ES_EVENT_TYPE_NOTIFY_OPEN) for sandboxed processes performing operations outside their typical behavioral baseline.
• Hunt for processes with the com.apple.security.app-sandbox entitlement that access user data directories, keychain items, or system locations inconsistent with their declared profile.
• Correlate sandboxd log entries showing repeated denials immediately preceding successful sensitive operations from the same process identifier.

Monitoring Recommendations

• Enable unified logging collection for the com.apple.sandbox and com.apple.xpc subsystems and forward to a central analytics platform.
• Baseline parent-child process relationships for sandboxed applications and alert on deviations.
• Track macOS build versions across the fleet to identify endpoints still running pre-patch releases of Sequoia, Sonoma, or Tahoe.

How to Mitigate CVE-2026-28817

Immediate Actions Required

• Update macOS Sequoia endpoints to 15.7.5 or later.
• Update macOS Sonoma endpoints to 14.8.5 or later.
• Update macOS Tahoe endpoints to 26.4 or later.
• Prioritize updates on systems that run untrusted code in sandboxed applications, including developer workstations and shared multi-user Macs.

Patch Information

Apple has released fixes in macOS Sequoia 15.7.5, macOS Sonoma 14.8.5, and macOS Tahoe 26.4. Refer to the vendor advisories for full update details: Apple Support Document #126794, Apple Support Document #126795, and Apple Support Document #126796.

Workarounds

• No vendor-supplied workaround exists. Apply the official patches.
• Restrict installation and execution of untrusted sandboxed applications on managed Macs through Mobile Device Management (MDM) policies until patches are deployed.
• Enforce Gatekeeper and notarization requirements to reduce exposure to untrusted code that could leverage this race condition.

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

# Trigger an MDM-managed software update check (Sequoia and later)
sudo softwareupdate --list
sudo softwareupdate --install --all --restart