CVE-2023-21964
📋 TL;DR
This vulnerability in Oracle WebLogic Server allows unauthenticated attackers with network access via the T3 protocol to cause a denial of service by crashing or hanging the server. It affects WebLogic Server versions 12.2.1.3.0, 12.2.1.4.0, and 14.1.1.0.0. Organizations running these versions with T3 enabled are at risk.
💻 Affected Systems
- Oracle WebLogic Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete unavailability of WebLogic Server, disrupting all applications and services hosted on it.
Likely Case
Service disruption causing application downtime and business impact.
If Mitigated
Minimal impact if T3 protocol is disabled or network access is restricted.
🎯 Exploit Status
Easily exploitable via network access to T3 port (typically 7001).
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Apply patches from Oracle Critical Patch Update April 2023
Vendor Advisory: https://www.oracle.com/security-alerts/cpuapr2023.html
Restart Required: Yes
Instructions:
1. Download appropriate patches from Oracle Support. 2. Apply patches following Oracle's patch installation procedures. 3. Restart WebLogic Server instances.
🔧 Temporary Workarounds
Disable T3 Protocol
allBlock or disable T3 protocol to prevent exploitation
Configure WebLogic to disable T3: set weblogic.security.net.ConnectionFilterImpl to filter T3 traffic
Use firewall rules to block port 7001/tcp
Network Segmentation
allRestrict network access to WebLogic T3 port
iptables -A INPUT -p tcp --dport 7001 -j DROP (Linux)
netsh advfirewall firewall add rule name="Block WebLogic T3" dir=in action=block protocol=TCP localport=7001 (Windows)
🧯 If You Can't Patch
- Implement strict network access controls to limit T3 protocol exposure
- Monitor for unusual T3 traffic patterns and server crash events
🔍 How to Verify
Check if Vulnerable:
Check WebLogic version and verify if running affected versions: 12.2.1.3.0, 12.2.1.4.0, or 14.1.1.0.0Check Version:
java weblogic.version (from WebLogic installation directory)Verify Fix Applied:
Verify patch installation via Oracle OPatch utility and confirm version is no longer vulnerable📡 Detection & Monitoring
Log Indicators:
- WebLogic server crash logs
- OutOfMemory errors in server logs
- Abnormal T3 connection attempts
Network Indicators:
- Unusual T3 protocol traffic patterns
- Multiple connection attempts to port 7001
SIEM Query:
source="weblogic.log" AND ("OutOfMemoryError" OR "Server shutdown" OR "T3 protocol error")