CVE-2009-3721
📋 TL;DR
This vulnerability allows attackers to exploit directory traversal and buffer overflow flaws in yTNEF and Evolution's TNEF parser when processing specially crafted email attachments. Successful exploitation could lead to arbitrary file writes, application crashes, or remote code execution. Affected users include those running vulnerable versions of yTNEF or Evolution email clients that process TNEF attachments.
💻 Affected Systems
- yTNEF
- Evolution email client
📦 What is this software?
Ytnef by Ytnef Project
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with the privileges of the email client user, potentially leading to full system compromise.
Likely Case
Application crash or denial of service when processing malicious TNEF attachments.
If Mitigated
Limited impact if email filtering blocks TNEF attachments or if applications run with restricted privileges.
🎯 Exploit Status
Exploitation requires user interaction to open malicious email attachments.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: yTNEF 1.5 or later, Evolution with updated TNEF parser
Vendor Advisory: http://www.ocert.org/advisories/ocert-2009-013.html
Restart Required: Yes
Instructions:
1. Update yTNEF to version 1.5 or later via package manager. 2. Update Evolution email client to latest patched version. 3. Restart affected applications.
🔧 Temporary Workarounds
Block TNEF attachments
linuxConfigure email filters to block or quarantine TNEF attachments at the mail server level.
# Example for Postfix: Use content_filter to scan attachments
# Example for amavisd: $ban_tnef = 1;
Disable TNEF processing
linuxConfigure Evolution to disable TNEF attachment processing if possible.
🧯 If You Can't Patch
- Implement strict email filtering to block all TNEF attachments at perimeter.
- Run email clients with reduced privileges and in sandboxed environments.
🔍 How to Verify
Check if Vulnerable:
Check installed yTNEF version: 'ytnef --version' or 'dpkg -l | grep ytnef'. For Evolution, check version via 'evolution --version'.Check Version:
ytnef --version 2>/dev/null || dpkg -l | grep ytnef || rpm -q ytnefVerify Fix Applied:
Confirm yTNEF version is 1.5 or later and Evolution has been updated to latest version from vendor repositories.📡 Detection & Monitoring
Log Indicators:
- Application crashes in Evolution or yTNEF processes
- Error logs mentioning TNEF parsing failures
Network Indicators:
- Inbound emails with TNEF attachments from untrusted sources
SIEM Query:
source="*mail.log" AND "TNEF" OR source="*syslog" AND ("ytnef" OR "evolution") AND ("crash" OR "segfault")