CVE-2025-29801: Microsoft AutoUpdate Privilege Escalation

CVE-2025-29801 Overview

CVE-2025-29801 is a local privilege escalation vulnerability in Microsoft AutoUpdate (MAU) on macOS. The flaw stems from incorrect default permissions [CWE-276] on components used by the update mechanism. An authenticated local attacker can abuse these permissions to elevate privileges on an affected host. Microsoft assigned the issue a CVSS 3.1 base score of 7.8 and addressed it through the Microsoft Security Response Center advisory.

Critical Impact
A local attacker with low privileges can gain high-integrity code execution on macOS systems running vulnerable versions of Microsoft AutoUpdate, resulting in full confidentiality, integrity, and availability impact.

Affected Products

Microsoft AutoUpdate (MAU) for macOS
macOS endpoints with Microsoft 365 or Office applications relying on MAU
Managed macOS fleets using MAU as the update transport

Discovery Timeline

2025-04-08 - CVE-2025-29801 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-29801

Vulnerability Analysis

Microsoft AutoUpdate is the update service that ships Microsoft 365 applications on macOS. It runs privileged helper components to install signed update payloads on the system. The vulnerability arises because files or directories used by MAU are created with permissions that grant write access to unprivileged local users. A local attacker who can log in to the host can modify content that is later executed or trusted by a higher-privileged process.

Successful exploitation results in code execution in the context of the privileged updater. That context typically maps to root on macOS, giving the attacker full control of the endpoint. The issue does not require user interaction and is scored as having low attack complexity.

Root Cause

The root cause is Incorrect Default Permissions [CWE-276]. Resources deployed by MAU inherit permissions that allow modification by users who should not have write access. When the update workflow later reads, loads, or executes those resources with elevated rights, the attacker's changes are honored. This is a classic privileged-file-permission flaw rather than a memory-safety defect.

Attack Vector

The attack vector is local. The attacker must already have valid credentials on the macOS system and the ability to execute code as a standard user. From that position, the attacker writes to a MAU-owned path that lacks proper ownership or mode restrictions. Triggering the update helper causes the tampered artifact to be executed with elevated privileges. See the Microsoft Security Update Guide for CVE-2025-29801 for vendor-supplied technical details.

Detection Methods for CVE-2025-29801

Indicators of Compromise

Unexpected file writes by non-privileged users under Microsoft AutoUpdate directories such as /Library/Application Support/Microsoft/ and MAU helper paths
Modifications to MAU binaries, plists, or scripts whose owner is not root:wheel
Launch of MAU helper processes such as Microsoft Update Assistant.app or Microsoft AutoUpdate.app followed by a privileged child process performing unusual actions
New LaunchDaemons or LaunchAgents installed shortly after MAU activity

Detection Strategies

Baseline the on-disk permissions of MAU components and alert on drift, especially world-writable or user-writable files under system paths.
Correlate standard-user file writes to MAU paths with subsequent privileged process execution using EDR process-lineage telemetry.
Hunt for privilege transitions where a root-owned MAU helper spawns shells, osascript, or other interpreters.

Monitoring Recommendations

Ingest macOS Endpoint Security (ES_EVENT_TYPE_NOTIFY_WRITE, EXEC) telemetry into a central data lake and pivot on MAU paths.
Monitor installed MAU versions across the fleet through MDM inventory and flag hosts running builds prior to the Microsoft-provided fix.
Track authentication and console-session events on macOS hosts to identify the local user context preceding suspicious MAU activity.

How to Mitigate CVE-2025-29801

Immediate Actions Required

Update Microsoft AutoUpdate to the fixed version identified in the Microsoft Security Update Guide for CVE-2025-29801.
Inventory macOS endpoints for MAU version and prioritize multi-user systems, shared workstations, and developer machines.
Restrict interactive local logon on servers or shared macOS hosts where MAU is installed.

Patch Information

Microsoft addressed the incorrect default permissions in an updated release of Microsoft AutoUpdate distributed through MAU itself and through Microsoft 365 admin channels. Administrators should confirm the deployed MAU build matches or exceeds the fixed version listed in the vendor advisory. Fleet-managed hosts should receive the update through MDM configuration profiles that force MAU to check in and apply pending updates.

Workarounds

Enforce least-privilege on macOS endpoints so that standard users cannot execute local exploitation primitives.
Use MDM to lock down write access to Microsoft application directories and restrict who can invoke MAU helper binaries.
Where patching is delayed, remove or disable Microsoft AutoUpdate on hosts that do not require self-service updates and manage Office updates through centrally deployed packages.

bash

# Check installed Microsoft AutoUpdate version on macOS
defaults read "/Library/Application Support/Microsoft/MAU2.0/Microsoft AutoUpdate.app/Contents/Info.plist" CFBundleShortVersionString

# Verify ownership and permissions of MAU components
ls -laO "/Library/Application Support/Microsoft/MAU2.0/"

# Compare against expected owner root:wheel and non-world-writable modes
sudo find "/Library/Application Support/Microsoft" -type f \( -perm -o+w -o -perm -g+w \) -print