CVE-2021-44549
📋 TL;DR
Apache Sling Commons Messaging Mail versions before 2.0 lack server identity verification for SMTPS connections by default, allowing man-in-the-middle attacks that could intercept or modify email communications. This affects systems using Apache Sling Commons Messaging Mail 1.0 to send emails via SMTPS without additional security configurations.
💻 Affected Systems
- Apache Sling Commons Messaging Mail
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers intercept sensitive email communications, steal credentials, inject malicious content, or redirect emails to attacker-controlled servers.
Likely Case
Email interception leading to data leakage, credential theft, or email content manipulation in environments with network-level attackers.
If Mitigated
Minimal impact with proper server identity verification enabled and network segmentation in place.
🎯 Exploit Status
Exploitation requires network-level access to intercept SMTPS traffic between vulnerable system and mail server.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apache Sling Commons Messaging Mail 2.0
Vendor Advisory: https://lists.apache.org/thread/l8p9h2bqvkj6rhv4w8kzctb817415b7f
Restart Required: Yes
Instructions:
1. Upgrade to Apache Sling Commons Messaging Mail 2.0 or later. 2. Restart the application/service. 3. Verify server identity checks are enabled (default in version 2.0).
🔧 Temporary Workarounds
Enable server identity checks manually
allManually set mail.smtps.ssl.checkserveridentity property to true in SimpleMessageBuilder configuration
Set JavaMail property: mail.smtps.ssl.checkserveridentity=true
🧯 If You Can't Patch
- Implement network segmentation to isolate email traffic from untrusted networks
- Use VPN or dedicated secure channels for email server communications
🔍 How to Verify
Check if Vulnerable:
Check if using Apache Sling Commons Messaging Mail version 1.0 or earlier with SMTPS connections without explicit server identity verification.Check Version:
Check Maven dependencies or OSGi bundle version for org.apache.sling.commons.messaging.mailVerify Fix Applied:
Verify version is 2.0 or later, and confirm mail.smtps.ssl.checkserveridentity property is set to true in configuration.📡 Detection & Monitoring
Log Indicators:
- Failed SSL/TLS handshakes with mail servers
- Unexpected certificate validation errors
Network Indicators:
- Unencrypted email traffic interception attempts
- SSL/TLS certificate mismatches in network monitoring
SIEM Query:
Search for JavaMail exceptions related to SSL/TLS validation or certificate verification failures