CVE-2021-43940
📋 TL;DR
This CVE describes a DLL hijacking vulnerability in Atlassian Confluence Server and Data Center installers on Windows. Authenticated local attackers can exploit this to elevate privileges on the local system. Only Windows installations running affected versions are vulnerable.
💻 Affected Systems
- Atlassian Confluence Server
- Atlassian Confluence Data Center
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An authenticated local attacker gains SYSTEM-level privileges, enabling complete compromise of the Windows host where Confluence is installed.
Likely Case
An authenticated user with local access escalates privileges to install malware, access sensitive data, or pivot to other systems.
If Mitigated
With proper access controls and monitoring, impact is limited to the local Confluence service account, preventing full system compromise.
🎯 Exploit Status
Requires authenticated local access to the Windows server. DLL hijacking is a well-known technique with established exploitation methods.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 7.4.10 or 7.12.3 and later
Vendor Advisory: https://jira.atlassian.com/browse/CONFSERVER-66550
Restart Required: Yes
Instructions:
1. Backup your Confluence instance. 2. Upgrade to Confluence Server/Data Center 7.4.10 or 7.12.3+. 3. Restart the Confluence service. 4. Verify the upgrade was successful.
🔧 Temporary Workarounds
Restrict local access
windowsLimit local login access to Confluence Windows servers to only necessary administrative users.
Monitor DLL loading
windowsImplement monitoring for suspicious DLL loading from non-standard locations in Confluence directories.
🧯 If You Can't Patch
- Implement strict access controls to prevent unauthorized local access to Confluence Windows servers
- Deploy endpoint detection and response (EDR) solutions to monitor for DLL hijacking behavior
🔍 How to Verify
Check if Vulnerable:
Check Confluence version via Admin > General Configuration. If version is before 7.4.10 or between 7.5.0-7.12.2 on Windows, the system is vulnerable.Check Version:
Check Confluence web interface at Admin > General Configuration or examine confluence/WEB-INF/classes/build.properties fileVerify Fix Applied:
After patching, confirm version is 7.4.10+ or 7.12.3+ via Admin > General Configuration.📡 Detection & Monitoring
Log Indicators:
- Windows Event Logs showing DLL loading from unusual locations
- Confluence logs showing unexpected process execution
Network Indicators:
- Unusual outbound connections from Confluence server post-exploitation
SIEM Query:
Windows Event ID 7 (Image loaded) with Confluence process loading DLLs from user-writable directories