CVE-2021-20354
📋 TL;DR
CVE-2021-20354 is a directory traversal vulnerability in IBM WebSphere Application Server that allows remote attackers to read arbitrary files on the system by sending specially crafted URL requests containing directory traversal sequences. This affects IBM WebSphere Application Server versions 8.0, 8.5, and 9.0.
💻 Affected Systems
- IBM WebSphere Application Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers could read sensitive system files including configuration files, credentials, and application source code, potentially leading to complete system compromise.
Likely Case
Attackers would read configuration files and sensitive data, enabling further attacks like credential theft and privilege escalation.
If Mitigated
With proper network segmentation and access controls, impact would be limited to reading non-sensitive files within the WebSphere directory.
🎯 Exploit Status
Exploitation requires only HTTP requests with directory traversal sequences.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply Interim Fix PI99848 or later cumulative fix
Vendor Advisory: https://www.ibm.com/support/pages/node/6415959
Restart Required: Yes
Instructions:
1. Download the appropriate interim fix from IBM Fix Central. 2. Stop all WebSphere servers. 3. Apply the fix using IBM Installation Manager. 4. Restart all servers.
🔧 Temporary Workarounds
URL Filtering
allConfigure web server or application firewall to block requests containing directory traversal sequences
File System Permissions
linuxRestrict WebSphere process permissions to limit accessible directories
chmod 750 /path/to/sensitive/directories
chown wasadmin:wasgroup /path/to/websphere
🧯 If You Can't Patch
- Implement strict network segmentation to isolate WebSphere servers from sensitive systems
- Deploy web application firewall with directory traversal protection rules
🔍 How to Verify
Check if Vulnerable:
Test by sending HTTP request with directory traversal sequences to WebSphere server and checking for file disclosureCheck Version:
$WAS_HOME/bin/versionInfo.shVerify Fix Applied:
Verify interim fix PI99848 is installed and test that directory traversal requests no longer return file contents📡 Detection & Monitoring
Log Indicators:
- HTTP requests containing '/../' patterns in access logs
- Unusual file access patterns from WebSphere process
Network Indicators:
- HTTP requests with multiple directory traversal sequences
- Responses containing file contents that shouldn't be accessible
SIEM Query:
source="websphere_access.log" AND "%2F..%2F" OR "/../"