CVE-2020-13376
📋 TL;DR
This vulnerability in SecurEnvoy SecurMail 9.3.503 allows attackers to upload executable files via a crafted cookie, leading to remote command execution on the underlying operating system. It affects organizations using the vulnerable version of SecurEnvoy's email security product.
💻 Affected Systems
- SecurEnvoy SecurMail
📦 What is this software?
Securmail by Securenvoy
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over the server, data exfiltration, lateral movement, and persistent backdoor installation.
Likely Case
Remote code execution leading to data theft, service disruption, or deployment of ransomware/malware.
If Mitigated
Limited impact with proper network segmentation, but still potential for initial foothold in the environment.
🎯 Exploit Status
Exploitation requires crafting a specific cookie value to trigger file upload and path traversal.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 9.3.504 or later
Vendor Advisory: https://www.securenvoy.com/en-gb/support
Restart Required: Yes
Instructions:
1. Contact SecurEnvoy support for patch 2. Apply patch following vendor instructions 3. Restart SecurMail service 4. Verify fix is applied
🔧 Temporary Workarounds
Cookie Validation Filter
allImplement web application firewall or reverse proxy rules to validate and sanitize SecurEnvoyReply cookie values
File Upload Restriction
windowsConfigure SecurMail to restrict uploads to non-executable file types only
🧯 If You Can't Patch
- Isolate SecurMail server in a DMZ with strict inbound/outbound firewall rules
- Implement network segmentation to limit lateral movement from compromised server
🔍 How to Verify
Check if Vulnerable:
Check SecurMail version in administrative interface - if version is 9.3.503, system is vulnerableCheck Version:
Check SecurMail web interface > About or System InformationVerify Fix Applied:
Verify version is updated to 9.3.504 or later in administrative interface📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads via SecurMail interface
- Suspicious SecurEnvoyReply cookie values in web logs
- Unexpected process execution on SecurMail server
Network Indicators:
- Unusual outbound connections from SecurMail server
- File uploads to unexpected locations
SIEM Query:
source="securenvoy" AND (cookie="SecurEnvoyReply" OR path="*upload*")🔗 References
- https://sidechannel.tempestsi.com/path-traversal-vulnerability-in-securenvoy-impacts-on-remote-command-execution-through-file-upload-ec2e731bd50a
- https://www.securenvoy.com/en-gb/support
- https://sidechannel.tempestsi.com/path-traversal-vulnerability-in-securenvoy-impacts-on-remote-command-execution-through-file-upload-ec2e731bd50a
- https://www.securenvoy.com/en-gb/support
