CVE-2021-27771
📋 TL;DR
CVE-2021-27771 is a path traversal vulnerability in HCL Sametime chat application where attackers can modify user session IDs to upload arbitrary files or delete directories. This can lead to remote code execution or denial of service. Affected systems are those running vulnerable versions of HCL Sametime.
💻 Affected Systems
- HCL Sametime
📦 What is this software?
Sametime by Hcltech
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution via arbitrary file upload leading to complete system compromise
Likely Case
Denial of service through directory deletion or file system corruption
If Mitigated
Limited impact with proper network segmentation and file system permissions
🎯 Exploit Status
Requires valid user session but exploitation is straightforward once session is obtained
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 11.6 Fix Pack 2 or later
Vendor Advisory: https://support.hcltechsw.com/csm?id=kb_article&sysparm_article=KB0097430
Restart Required: Yes
Instructions:
1. Download HCL Sametime 11.6 Fix Pack 2 or later from HCL support portal. 2. Apply the fix pack following HCL documentation. 3. Restart Sametime services.
🔧 Temporary Workarounds
Restrict file upload permissions
allLimit file system permissions for Sametime service account to prevent arbitrary file writes
Network segmentation
allIsolate Sametime servers from critical systems and implement strict firewall rules
🧯 If You Can't Patch
- Implement strict access controls and monitor for unusual file upload activities
- Deploy web application firewall with path traversal protection rules
🔍 How to Verify
Check if Vulnerable:
Check Sametime version via administrative console or version files in installation directoryCheck Version:
Check version.txt in Sametime installation directory or use administrative interfaceVerify Fix Applied:
Verify version is 11.6 Fix Pack 2 or later and test file upload functionality📡 Detection & Monitoring
Log Indicators:
- Unusual file upload patterns
- Path traversal attempts in file transfer logs
- Directory deletion events
Network Indicators:
- Abnormal file transfer sizes or patterns
- Multiple failed upload attempts
SIEM Query:
source="sametime.log" AND ("..\" OR "../" OR "path traversal" OR "directory traversal")