CVE-2026-39874 Overview
CVE-2026-39874 is a local privilege escalation vulnerability in Apple macOS caused by an incorrect default permissions issue [CWE-276]. A malicious application running on an affected system can exploit this flaw to gain root privileges. Apple addressed the issue by applying additional permission restrictions in macOS Sequoia 15.7.8, macOS Sonoma 14.8.8, and macOS Tahoe 26.6.
The vulnerability requires local access and low privileges, but no user interaction. Successful exploitation results in full compromise of confidentiality, integrity, and availability on the target host.
Critical Impact
A malicious app installed on an unpatched macOS system can escalate to root, giving full control of the device.
Affected Products
- Apple macOS Sequoia versions prior to 15.7.8
- Apple macOS Sonoma versions prior to 14.8.8
- Apple macOS Tahoe versions prior to 26.6
Discovery Timeline
- 2026-07-27 - CVE-2026-39874 published to NVD
- 2026-07-29 - Last updated in NVD database
Technical Details for CVE-2026-39874
Vulnerability Analysis
CVE-2026-39874 is classified as an Incorrect Default Permissions weakness [CWE-276]. A macOS component ships with permission settings that permit an unprivileged local process to perform operations reserved for privileged users. Apple's advisory describes the fix as adding restrictions to close this gap.
Because the flaw is local, an attacker must first execute code on the system, typically through a malicious application, a trojanized installer, or a compromised developer tool. Once running as a standard user, the malicious process can leverage the over-permissive resource to escalate to root without triggering interactive prompts.
Root-level access on macOS bypasses System Integrity Protection boundaries reserved for administrators and enables tampering with security controls, installation of persistent implants, and access to protected user data.
Root Cause
The root cause is a permissions misconfiguration in a macOS system component. Apple has not published the specific component name in the public advisory. The vendor patch narrows the permission scope so that unprivileged processes can no longer invoke the affected functionality.
Attack Vector
Exploitation requires local code execution on the target Mac with any authenticated user context. No user interaction is required after the malicious code runs. The attack complexity is low, meaning a reliable exploit is achievable without specialized conditions. Consult the Apple Security Advisory 128067, Apple Security Advisory 128071, and Apple Security Advisory 128072 for vendor guidance.
Detection Methods for CVE-2026-39874
Indicators of Compromise
- Unexpected processes running as root that were spawned by user-owned applications or LaunchAgents.
- New or modified files under /Library/LaunchDaemons/, /private/etc/, or /usr/local/ created by non-administrative user sessions.
- Unsigned or ad-hoc-signed binaries invoking privileged system services shortly after a standard user login.
Detection Strategies
- Monitor Endpoint Security framework (ES) events for ES_EVENT_TYPE_NOTIFY_EXEC transitions where the effective UID changes to 0 without a legitimate sudo or authorization prompt.
- Alert on modifications to files and directories protected by macOS permissions when the acting process is not a signed Apple binary.
- Correlate installer activity from unknown developer IDs with subsequent privileged file writes or launchctl load operations.
Monitoring Recommendations
- Ingest unified log data (log stream predicates on authd, securityd, and tccd) into a centralized analytics platform for retrospective hunting.
- Track macOS build numbers across the fleet and flag hosts still running versions below 15.7.8, 14.8.8, or 26.6.
- Baseline privileged process trees per endpoint and alert on deviations, especially root processes with user-writable parent binaries.
How to Mitigate CVE-2026-39874
Immediate Actions Required
- Update all Macs to macOS Sequoia 15.7.8, macOS Sonoma 14.8.8, or macOS Tahoe 26.6 as applicable.
- Restrict installation of unsigned or unnotarized applications through Gatekeeper policy and MDM configuration profiles.
- Audit endpoints for third-party applications requesting elevated privileges or Full Disk Access without a documented business need.
Patch Information
Apple released fixes in macOS Sequoia 15.7.8, macOS Sonoma 14.8.8, and macOS Tahoe 26.6. See Apple Security Advisory 128067, Apple Security Advisory 128071, and Apple Security Advisory 128072 for the full list of addressed issues and download links. Deploy the updates through Apple Software Update or an enterprise MDM such as Jamf, Kandji, or Intune.
Workarounds
- No vendor-supplied workaround exists; patching is the supported remediation path.
- Reduce exposure by enforcing standard-user accounts for daily use and reserving administrator credentials for privileged tasks.
- Block execution of untrusted applications with Gatekeeper set to "App Store and identified developers" or stricter, combined with allowlisting via MDM.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
