CVE-2021-24114: Microsoft Teams iOS Info Disclosure Flaw

CVE-2021-24114 Overview

CVE-2021-24114 is an Information Disclosure vulnerability affecting Microsoft Teams for iOS. This vulnerability allows an authenticated attacker to potentially access sensitive information through the Microsoft Teams iOS application when user interaction occurs. The flaw enables unauthorized disclosure of confidential data that could be leveraged for further attacks or reconnaissance activities.

Critical Impact

Authenticated attackers can exploit this vulnerability to gain access to sensitive information in Microsoft Teams iOS, potentially compromising organizational communications and data confidentiality.

Affected Products

• Microsoft Teams for iOS (iPhone OS)

Discovery Timeline

• 2021-02-25 - CVE CVE-2021-24114 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-24114

Vulnerability Analysis

This Information Disclosure vulnerability in Microsoft Teams for iOS stems from improper handling of sensitive data within the mobile application. The vulnerability requires an authenticated attacker with low privileges and some form of user interaction to successfully exploit. Upon successful exploitation, an attacker gains the ability to access confidential information with high impact to data confidentiality, while integrity and availability remain unaffected.

The network-based attack vector combined with low complexity makes this vulnerability relatively accessible to attackers who have already obtained valid credentials. The requirement for user interaction provides some mitigation, as exploitation cannot occur in a fully automated fashion without target engagement.

Root Cause

The exact root cause has not been publicly disclosed by Microsoft. Based on the vulnerability classification (NVD-CWE-noinfo), the specific technical flaw leading to information disclosure has not been detailed. Information Disclosure vulnerabilities in mobile applications typically arise from improper data handling, insecure storage mechanisms, or inadequate access controls that allow authenticated users to access data beyond their authorization scope.

Attack Vector

The attack vector is network-based, requiring the attacker to have authenticated access to Microsoft Teams. The exploitation scenario involves:

1. Attacker obtains valid authentication credentials for Microsoft Teams
2. Attacker targets a user and requires some form of interaction
3. Through the vulnerability, the attacker gains access to sensitive information they should not have authorization to view

The requirement for user interaction suggests this may involve social engineering tactics or requires the victim to perform a specific action within the Teams application.

Due to the sensitive nature of this vulnerability and the lack of publicly disclosed technical details, no verified proof-of-concept code is available. For technical implementation details, refer to the Microsoft Security Advisory CVE-2021-24114.

Detection Methods for CVE-2021-24114

Indicators of Compromise

• Unusual authentication patterns or access attempts from unfamiliar devices targeting Microsoft Teams iOS users
• Anomalous data access patterns within Microsoft Teams that deviate from normal user behavior
• Reports of sensitive information being accessed or disclosed outside authorized channels
• Unexpected network traffic originating from Microsoft Teams iOS application

Detection Strategies

• Monitor Microsoft 365 audit logs for suspicious access patterns related to Teams iOS clients
• Implement mobile device management (MDM) solutions to track application versions and detect outdated Teams installations
• Review authentication logs for anomalous login attempts or credential usage patterns
• Enable and monitor Microsoft Cloud App Security for unusual activity detection

Monitoring Recommendations

• Configure alerting for Microsoft Teams data access anomalies through Microsoft 365 Security Center
• Establish baseline behavior patterns for Teams iOS usage and alert on deviations
• Monitor for users accessing Teams data they have not historically accessed
• Track application version deployment across iOS devices to identify unpatched installations

How to Mitigate CVE-2021-24114

Immediate Actions Required

• Update Microsoft Teams iOS application to the latest version available in the App Store
• Review and audit sensitive information that may have been accessed through Teams iOS
• Enforce mobile device management policies requiring up-to-date application versions
• Implement conditional access policies limiting Teams access to compliant devices

Patch Information

Microsoft has addressed this vulnerability through application updates. Organizations should ensure all iOS devices running Microsoft Teams are updated to the latest available version. For detailed patch and remediation guidance, refer to the Microsoft Security Advisory CVE-2021-24114.

Workarounds

• Restrict access to sensitive Teams channels and data for users on potentially vulnerable iOS devices
• Implement additional authentication requirements (MFA) for accessing sensitive information through Teams
• Consider using web-based Teams access on iOS as a temporary measure until devices are patched
• Limit data sharing and retention policies within Teams to minimize exposure of sensitive information

# Verify Microsoft Teams iOS version compliance via MDM
# Example: Intune compliance policy configuration
# Minimum app version should be set to the patched release
# Refer to Microsoft documentation for specific version requirements