CVE-2021-20584
📋 TL;DR
IBM Sterling File Gateway versions 2.2.0.0 through 6.1.1.0 have an improper access control vulnerability that allows remote attackers to upload arbitrary files. This could lead to unauthorized file system access, data manipulation, or further system compromise. Organizations using these versions of IBM Sterling File Gateway are affected.
💻 Affected Systems
- IBM Sterling File Gateway
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote attacker gains full control of the file gateway system, uploads malicious files (webshells, malware), executes arbitrary code, accesses sensitive data, and pivots to other internal systems.
Likely Case
Attacker uploads malicious files to compromise the file gateway service, potentially stealing or manipulating business files, disrupting file transfer operations, and establishing persistence.
If Mitigated
With proper network segmentation and access controls, impact is limited to the file gateway system itself, preventing lateral movement and protecting sensitive backend systems.
🎯 Exploit Status
The vulnerability requires some level of access to the file gateway interface, but improper access controls make exploitation straightforward once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply interim fix or upgrade to version 6.1.1.1 or later
Vendor Advisory: https://www.ibm.com/support/pages/node/6496751
Restart Required: Yes
Instructions:
1. Download the interim fix from IBM Fix Central. 2. Stop the Sterling File Gateway service. 3. Apply the fix according to IBM instructions. 4. Restart the service. 5. Verify the fix is applied.
🔧 Temporary Workarounds
Restrict Network Access
allLimit access to the Sterling File Gateway interface to only trusted IP addresses/networks.
Use firewall rules to restrict access to Sterling File Gateway ports (typically 9080, 9443)
Implement File Upload Validation
allAdd additional file type validation and scanning for uploaded files.
Configure Sterling File Gateway to only accept specific file types and implement antivirus scanning
🧯 If You Can't Patch
- Isolate the Sterling File Gateway system in a DMZ or segmented network zone
- Implement strict access controls and multi-factor authentication for all administrative access
🔍 How to Verify
Check if Vulnerable:
Check the Sterling File Gateway version via the administrative console or by examining installation files. Versions 2.2.0.0 through 6.1.1.0 are vulnerable.Check Version:
Check the version in the Sterling File Gateway administrative interface or review the product documentation for version information.Verify Fix Applied:
Verify the version is 6.1.1.1 or later, or confirm the interim fix is applied via the IBM Fix Central verification process.📡 Detection & Monitoring
Log Indicators:
- Unusual file upload patterns
- Unauthorized access attempts to file upload endpoints
- Files with suspicious extensions being uploaded
Network Indicators:
- Unusual traffic to file upload endpoints from unexpected sources
- Large or frequent file uploads from single sources
SIEM Query:
source="sterling_gateway" AND (event="file_upload" AND (file_extension="jsp" OR file_extension="php" OR file_extension="exe"))