CVE-2026-43783: Apple macOS Race Condition Vulnerability

CVE-2026-43783 Overview

CVE-2026-43783 is a race condition vulnerability in Apple macOS that allows a malicious application to gain root privileges. The flaw stems from improper locking in a kernel or system component, creating a time-of-check to time-of-use (TOCTOU) window an attacker can exploit. Apple addressed the issue in macOS Tahoe 26.6 by introducing improved locking around the affected code path. The weakness is classified under [CWE-362] (Concurrent Execution using Shared Resource with Improper Synchronization).

Critical Impact
A local attacker running an unprivileged application can escalate to root, resulting in full compromise of confidentiality, integrity, and availability on the affected macOS host.

Affected Products

Apple macOS versions prior to macOS Tahoe 26.6
Systems running vulnerable macOS builds where the patch has not been applied
Any macOS device permitting installation of untrusted third-party applications

Discovery Timeline

2026-09-14 - CVE-2026-43783 published to the National Vulnerability Database
2026-09-15 - Last updated in NVD database

Technical Details for CVE-2026-43783

Vulnerability Analysis

The vulnerability is a race condition in a privileged macOS component. Two or more concurrent execution paths access a shared resource without adequate synchronization. An attacker who wins the race can influence the outcome of a security-sensitive operation performed at elevated privilege. The result is local privilege escalation from a standard user context to root.

Apple's advisory attributes the fix to "improved locking," indicating that the original code either omitted a lock, held a lock for insufficient duration, or allowed a state change between validation and use. See the Apple Support Article for the official disclosure.

Root Cause

The root cause is improper synchronization of concurrent execution using a shared resource [CWE-362]. Privileged code validated or referenced a resource whose state could be modified by another thread or process before the operation completed. This TOCTOU pattern permits substitution or corruption of the resource between check and use.

Attack Vector

Exploitation requires local access. An attacker must deliver and execute a malicious application on the target macOS system, typically through social engineering, a supply-chain vector, or an initial foothold. The application then runs concurrent operations designed to trigger the race window in the vulnerable component. No user interaction beyond running the malicious app is required. Successful exploitation yields root privileges, enabling installation of persistent implants, disabling of security controls, and access to protected data.

No public proof-of-concept exploit is currently listed in ExploitDB, and the vulnerability is not on the CISA Known Exploited Vulnerabilities catalog. Apple has not published low-level technical details of the affected component.

Detection Methods for CVE-2026-43783

Indicators of Compromise

Unexpected processes running as root that were spawned by user-level applications
New or modified files in privileged locations such as /Library/LaunchDaemons/, /System/Library/, or /private/etc/
Unsigned or ad-hoc-signed binaries executing with elevated entitlements
Repeated, rapid invocations of the same privileged system call from a single non-privileged process, consistent with race-condition brute-forcing

Detection Strategies

Monitor endpoint telemetry for privilege transitions where a non-privileged parent process spawns a child running as uid=0
Alert on installation of new LaunchDaemons, LaunchAgents, or kernel extensions outside of managed deployment channels
Correlate application execution events with subsequent modifications to protected system paths
Track macOS build versions across the fleet to identify hosts still running versions prior to macOS Tahoe 26.6

Monitoring Recommendations

Ingest macOS Endpoint Security Framework events into a centralized analytics platform for behavioral analysis
Baseline normal privileged operations per application and alert on deviations
Retain process ancestry, code-signing status, and entitlement data for forensic review
Review MDM inventory reports weekly to confirm patch adoption across managed macOS endpoints

How to Mitigate CVE-2026-43783

Immediate Actions Required

Update all affected macOS systems to macOS Tahoe 26.6 or later without delay
Prioritize patching on developer workstations and hosts with access to sensitive data or credentials
Restrict installation of untrusted applications through Gatekeeper policies and MDM configuration profiles
Audit recently installed applications and remove any that lack a legitimate business need

Patch Information

Apple fixed CVE-2026-43783 in macOS Tahoe 26.6 by introducing improved locking around the vulnerable code path. Administrators should apply the update via Software Update or through their MDM solution. Refer to the Apple Support Article for the complete list of addressed CVEs and installation guidance.

Workarounds

No vendor-supplied workaround exists; applying macOS Tahoe 26.6 is the authoritative fix
Reduce exposure by enforcing least-privilege user accounts and disallowing local administrator rights where not required
Enable and enforce Gatekeeper, System Integrity Protection (SIP), and notarization requirements for all executables
Use application allow-listing to prevent execution of unapproved binaries pending patch deployment

bash

# Verify current macOS build and confirm patch status
sw_vers

# Trigger macOS software update check from the command line
sudo softwareupdate --list
sudo softwareupdate --install --all --restart