CVE-2024-42004: Microsoft Teams Auth Bypass Vulnerability

CVE-2024-42004 Overview

A library injection vulnerability exists in Microsoft Teams (work or school) version 24046.2813.2770.1094 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 enables attackers to bypass macOS permission controls by hijacking Microsoft Teams' elevated privileges, potentially allowing unauthorized access to sensitive resources such as microphone, camera, and file system access that Teams has been granted.

Affected Products

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

Discovery Timeline

• 2024-12-18 - CVE-2024-42004 published to NVD
• 2025-08-26 - Last updated in NVD database

Technical Details for CVE-2024-42004

Vulnerability Analysis

This library injection vulnerability (CWE-347: Improper Verification of Cryptographic Signature) affects Microsoft Teams on macOS. The core issue stems from inadequate validation of dynamically loaded libraries, allowing malicious code to be injected into the Teams process space. When successfully exploited, the injected library inherits all permissions and entitlements granted to Microsoft Teams by the user or system administrator.

On macOS, applications like Microsoft Teams often require extensive permissions including access to the microphone, camera, screen recording, and file system locations. By injecting malicious code into the Teams process, an attacker can silently leverage these pre-approved permissions without triggering additional user consent dialogs.

Root Cause

The vulnerability originates from insufficient verification of library signatures and improper validation of dynamically loaded code. Microsoft Teams fails to adequately verify that libraries being loaded are legitimate and properly signed, allowing attackers to inject arbitrary code into the application's execution context. This weakness in cryptographic signature verification (CWE-347) enables the permission bypass attack.

Attack Vector

The attack requires a malicious application to be present on the target system. The attacker's application prepares a specially crafted dynamic library and uses library injection techniques specific to macOS to load it into the Microsoft Teams process. Once the malicious library is loaded and Teams is executed, the injected code runs with Teams' full privilege set, effectively bypassing macOS's permission model.

The attack mechanism involves:

1. A malicious application creates or deploys a crafted dynamic library (.dylib) on the target system
2. The attacker leverages macOS library injection mechanisms such as DYLD_INSERT_LIBRARIES or similar techniques
3. When Microsoft Teams launches, the malicious library is loaded into its address space
4. The injected code executes with all permissions previously granted to Microsoft Teams

Detection Methods for CVE-2024-42004

Indicators of Compromise

• Unexpected or unsigned dynamic libraries loaded by the Microsoft Teams process
• Unusual DYLD_* environment variables set for Teams processes
• Teams accessing resources inconsistent with normal user activity patterns
• Unfamiliar library files in directories accessible to the Teams application

Detection Strategies

• Monitor process execution for Microsoft Teams with suspicious environment variables or library preloading configurations
• Implement endpoint detection rules to identify unsigned or unexpected .dylib files being loaded by trusted applications
• Use macOS code signing verification tools to validate libraries loaded by Microsoft Teams
• Deploy behavioral analysis to detect Teams accessing resources without corresponding user interaction

Monitoring Recommendations

• Enable detailed logging for library loading events on macOS endpoints
• Monitor for changes to library paths and environment variables associated with Microsoft Teams
• Implement file integrity monitoring for Microsoft Teams application directories
• Configure alerts for Teams processes attempting to access sensitive resources outside normal business hours

How to Mitigate CVE-2024-42004

Immediate Actions Required

• Update Microsoft Teams to the latest available version that addresses this vulnerability
• Review and restrict permissions granted to Microsoft Teams to minimize potential impact
• Audit systems for unauthorized or unexpected dynamic libraries in application directories
• Implement application whitelisting to prevent unauthorized library loading

Patch Information

Microsoft has been notified of this vulnerability through responsible disclosure. Organizations should check for security updates from Microsoft and apply the latest version of Microsoft Teams for macOS. For detailed technical information, refer to the Talos Intelligence Vulnerability Report.

Workarounds

• Restrict which applications can modify Microsoft Teams' directory and library paths
• Use macOS Security Framework features to enforce stricter code signing requirements
• Consider implementing Hardened Runtime restrictions for third-party applications
• Deploy endpoint protection solutions capable of detecting library injection attempts
• Limit local administrator privileges to reduce the attack surface for library injection attacks

# Check for suspicious environment variables on macOS
# Run this command to identify any DYLD injection attempts
env | grep -i DYLD

# Verify code signing of Microsoft Teams
codesign -vvv --deep "/Applications/Microsoft Teams.app"

# List loaded libraries for Teams process (replace PID with actual process ID)
# sudo vmmap <PID> | grep -i dylib