CVE-2024-41138: Microsoft Teams Auth Bypass Vulnerability

CVE-2024-41138 Overview

A library injection vulnerability exists in the com.microsoft.teams2.modulehost.app helper app of Microsoft Teams (work or school) for macOS. This vulnerability allows a specially crafted library to leverage Teams's access privileges, leading to a permission bypass. A malicious application could inject a library and start the program to trigger this vulnerability, subsequently making use of the vulnerable application's permissions.

Critical Impact

This vulnerability allows attackers to bypass macOS permission controls by injecting malicious libraries into Microsoft Teams, potentially gaining access to sensitive resources including camera, microphone, and file system access that Teams has been granted.

Affected Products

• Microsoft Teams version 24046.2813.2770.1094 for macOS
• Microsoft Teams (work or school) for macOS

Discovery Timeline

• December 18, 2024 - CVE-2024-41138 published to NVD
• August 26, 2025 - Last updated in NVD database

Technical Details for CVE-2024-41138

Vulnerability Analysis

This library injection vulnerability affects the com.microsoft.teams2.modulehost.app helper application bundled with Microsoft Teams for macOS. The vulnerability stems from improper verification of cryptographic signatures (CWE-347), which allows malicious actors to inject unauthorized code into the application's runtime environment.

The impact of successful exploitation is significant on macOS systems where Microsoft Teams typically holds elevated permissions. Teams applications often have access to sensitive system resources including the camera, microphone, screen recording capabilities, and file system access. By injecting a malicious library, an attacker can inherit and abuse these permissions without triggering macOS security prompts or user consent dialogs.

The attack can be executed remotely over the network, requiring no privileges or user interaction, making it particularly dangerous in enterprise environments where Teams is widely deployed.

Root Cause

The root cause of this vulnerability lies in the improper verification of cryptographic signatures (CWE-347) within the com.microsoft.teams2.modulehost.app helper application. The helper app fails to adequately validate that loaded libraries are properly signed and authorized, allowing unsigned or maliciously signed code to be loaded and executed within the application's security context.

On macOS, applications that fail to enforce proper library validation can be exploited through dylib injection techniques. The Teams helper app does not implement sufficient hardened runtime protections or library validation checks, enabling attackers to hijack the application's entitlements and permissions.

Attack Vector

The attack vector for this vulnerability involves network-based exploitation with the following characteristics:

1. Initial Access: An attacker needs to place a malicious library on the target macOS system, which could be achieved through various means including social engineering, drive-by downloads, or exploitation of other vulnerabilities
2. Library Injection: The malicious library is crafted to be loaded by the com.microsoft.teams2.modulehost.app helper application
3. Permission Hijacking: Once loaded, the malicious code inherits all permissions previously granted to Microsoft Teams
4. Privilege Abuse: The attacker can then access camera, microphone, screen recording, file system, and other sensitive resources without triggering additional permission prompts

The vulnerability requires no user interaction and can be exploited without authentication, making it a high-priority security concern for organizations using Microsoft Teams on macOS.

Detection Methods for CVE-2024-41138

Indicators of Compromise

• Unexpected dylib files present in Microsoft Teams application directories or user-writable locations
• Unusual library load events associated with com.microsoft.teams2.modulehost.app
• Anomalous network connections originating from the Teams helper application
• Unauthorized access to camera, microphone, or screen recording initiated by Teams processes

Detection Strategies

• Monitor for dylib injection attempts targeting Microsoft Teams processes using Endpoint Detection and Response (EDR) solutions
• Implement file integrity monitoring on Microsoft Teams application bundles and associated directories
• Analyze process creation events and library loading activity for the com.microsoft.teams2.modulehost.app helper
• Deploy behavioral analysis to detect unusual permission usage patterns from Teams applications

Monitoring Recommendations

• Enable macOS Unified Logging for Library Validation and code signing events
• Monitor the /Applications/Microsoft Teams.app/ directory and subdirectories for unauthorized modifications
• Track TCC (Transparency, Consent, and Control) database access patterns for Teams-related processes
• Implement alerting for unusual child processes spawned by Microsoft Teams applications

How to Mitigate CVE-2024-41138

Immediate Actions Required

• Update Microsoft Teams for macOS to the latest available version immediately
• Review and audit permissions granted to Microsoft Teams in System Preferences > Privacy & Security
• Implement application whitelisting to prevent unauthorized library loading
• Consider temporarily restricting Microsoft Teams permissions until patching is complete in high-security environments

Patch Information

Organizations should update Microsoft Teams for macOS to a version newer than 24046.2813.2770.1094. The vulnerability was disclosed through Talos Intelligence Vulnerability Report TALOS-2024-1991. System administrators should check Microsoft's security advisories and update channels for the latest patched version of Teams for macOS.

Workarounds

• Restrict write access to directories where Microsoft Teams loads libraries to prevent malicious library placement
• Enable macOS hardened runtime enforcement and library validation through MDM policies where possible
• Implement network segmentation to limit potential attack vectors for initial malicious library delivery
• Deploy SentinelOne Singularity Platform to detect and block library injection attempts targeting Microsoft Teams

# Check current Microsoft Teams version on macOS
/Applications/Microsoft\ Teams.app/Contents/Info.plist | grep -A1 CFBundleShortVersionString

# Review Teams permissions in TCC database (requires admin)
sudo sqlite3 /Library/Application\ Support/com.apple.TCC/TCC.db "SELECT client,service FROM access WHERE client LIKE '%teams%';"

# Monitor for unauthorized library loading (example using fs_usage)
sudo fs_usage -w -f filesys | grep -i teams | grep dylib