CVE-2024-43106: Microsoft Excel Privilege Escalation

CVE-2024-43106 Overview

A library injection vulnerability exists in Microsoft Excel 16.83 for macOS that allows attackers to leverage Excel's elevated access privileges, leading to a permission bypass. A malicious application could inject a specially crafted library and start the program to trigger this vulnerability, subsequently making use of the vulnerable application's permissions. This DLL injection flaw enables attackers to execute arbitrary code within the context of Excel, potentially accessing sensitive data and system resources that Excel has been granted access to.

Critical Impact

This vulnerability allows attackers to bypass macOS permission controls by leveraging Microsoft Excel's existing access privileges, potentially enabling unauthorized access to protected resources like the camera, microphone, contacts, and file system.

Affected Products

• Microsoft Excel 16.83 for macOS
• Microsoft Excel for macOS (versions prior to security patch)

Discovery Timeline

• 2024-12-18 - CVE-2024-43106 published to NVD
• 2025-08-22 - Last updated in NVD database

Technical Details for CVE-2024-43106

Vulnerability Analysis

This library injection vulnerability (CWE-347) stems from improper verification of cryptographic signatures in Microsoft Excel for macOS. The application fails to properly validate the authenticity of dynamically loaded libraries, allowing malicious actors to inject unauthorized code into the Excel process. Once injected, the malicious library executes within Excel's security context, inheriting all permissions previously granted to the application by the user through macOS's Transparency, Consent, and Control (TCC) framework.

The attack is particularly concerning because macOS users often grant Microsoft Office applications broad permissions for functionality purposes, including access to protected resources. An attacker exploiting this vulnerability can silently access these resources without triggering additional permission prompts.

Root Cause

The root cause of this vulnerability lies in the improper verification of cryptographic signatures for dynamically loaded libraries. Microsoft Excel fails to adequately validate the authenticity and integrity of libraries before loading them into its process space. This oversight allows unsigned or maliciously signed libraries to be loaded and executed within the trusted context of the Excel application.

Attack Vector

The attack is initiated over the network and requires no user interaction or special privileges. An attacker can create a malicious library designed to exploit Excel's access privileges. When a malicious application injects this library and triggers Excel to load it, the injected code gains access to all permissions that Excel has been granted. This could include access to sensitive macOS resources such as:

• File system locations protected by TCC
• Camera and microphone access
• Contacts and calendar data
• Location services
• Accessibility features

The vulnerability exploits macOS's trust model, where permissions granted to a legitimate application like Excel can be abused by injected code running within that application's context.

Detection Methods for CVE-2024-43106

Indicators of Compromise

• Unexpected library files loaded by Microsoft Excel processes
• Unusual child processes spawned from Excel
• Suspicious dynamic library load events in macOS system logs
• Unauthorized access to TCC-protected resources from Excel process

Detection Strategies

• Monitor for unsigned or unexpectedly signed libraries being loaded by Microsoft Excel
• Implement endpoint detection for suspicious dyld library loading events
• Configure alerts for Excel accessing sensitive resources in unusual patterns
• Review system logs for library injection attempts targeting Office applications

Monitoring Recommendations

• Enable verbose logging for macOS dyld library loading events
• Monitor TCC database access patterns for anomalies
• Deploy behavioral analysis to detect permission abuse patterns
• Track process integrity for Microsoft Office applications on macOS endpoints

How to Mitigate CVE-2024-43106

Immediate Actions Required

• Update Microsoft Excel for macOS to the latest available version
• Review and audit permissions granted to Microsoft Office applications
• Implement application allowlisting to prevent unauthorized library loading
• Deploy endpoint protection solutions with library injection detection capabilities

Patch Information

Microsoft should be contacted directly for official patch information. Users should ensure automatic updates are enabled for Microsoft Office applications and verify they are running the latest version available. For detailed technical information about this vulnerability, refer to the Talos Intelligence Vulnerability Report.

Workarounds

• Restrict Microsoft Excel's macOS permissions to only essential functions
• Implement strict application control policies on managed devices
• Consider using Microsoft Office in a sandboxed environment
• Monitor and restrict network access for Excel to prevent remote exploitation attempts
• Review and minimize TCC permissions for Office applications where possible

# Review current TCC permissions for Excel on macOS
# Check database for Excel permissions
sqlite3 ~/Library/Application\ Support/com.apple.TCC/TCC.db "SELECT * FROM access WHERE client LIKE '%Excel%';"

# Monitor for suspicious library loading (requires elevated privileges)
log show --predicate 'process == "Microsoft Excel"' --info --last 1h