CVE-2021-21307
📋 TL;DR
CVE-2021-21307 is an unauthenticated remote code execution vulnerability in Lucee Server's admin interface. Attackers can exploit this to execute arbitrary code on affected servers without authentication. Organizations running vulnerable Lucee Server versions with exposed admin interfaces are affected.
💻 Affected Systems
- Lucee Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to install malware, steal data, pivot to other systems, or establish persistent backdoors.
Likely Case
Web server compromise leading to data theft, website defacement, or cryptocurrency mining malware installation.
If Mitigated
No impact if admin interface is properly firewalled or access controls are implemented.
🎯 Exploit Status
Exploit code is publicly available and requires minimal technical skill to execute.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.3.7.47, 5.3.6.68, or 5.3.5.96
Vendor Advisory: https://dev.lucee.org/t/lucee-vulnerability-alert-november-2020/7643
Restart Required: Yes
Instructions:
1. Backup your Lucee configuration and applications. 2. Download the patched version from lucee.org. 3. Stop the Lucee service. 4. Install the patched version. 5. Restart the Lucee service. 6. Verify the version is updated.
🔧 Temporary Workarounds
Block Admin Interface Access
allRestrict access to Lucee Administrator interface using firewall rules or web server configuration.
# Apache: Deny from all to /lucee/admin
# Nginx: location /lucee/admin { deny all; }
# Firewall: iptables -A INPUT -p tcp --dport 8888 -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation and firewall rules to block all external access to Lucee Admin interface
- Deploy web application firewall (WAF) rules to detect and block exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check if Lucee Admin interface is accessible at /lucee/admin and version is below patched versions.Check Version:
Check lucee-server.xml or visit /lucee/admin/server.cfm?action=serverVerify Fix Applied:
Verify Lucee version is 5.3.7.47, 5.3.6.68, or 5.3.5.96 or higher, and test that admin interface no longer accepts unauthenticated RCE attempts.📡 Detection & Monitoring
Log Indicators:
- Unusual file writes to web directories
- Access to imgProcess.cfm with suspicious parameters
- Unauthenticated requests to admin endpoints
Network Indicators:
- HTTP requests to /lucee/admin/imgProcess.cfm with file upload parameters
- Unusual outbound connections from web server
SIEM Query:
source="web_server" AND (uri="/lucee/admin/imgProcess.cfm" OR uri="/lucee/admin/*") AND status=200🔗 References
- http://ciacfug.org/blog/updating-lucee-as-part-of-a-vulnerability-alert-response
- http://packetstormsecurity.com/files/163864/Lucee-Administrator-imgProcess.cfm-Arbitrary-File-Write.html
- https://dev.lucee.org/t/lucee-vulnerability-alert-november-2020/7643
- https://github.com/httpvoid/writeups/blob/main/Apple-RCE.md
- https://github.com/lucee/Lucee/commit/6208ab7c44c61d26c79e0b0af10382899f57e1ca
- https://github.com/lucee/Lucee/security/advisories/GHSA-2xvv-723c-8p7r
- https://portswigger.net/daily-swig/security-researchers-earn-50k-after-exposing-critical-flaw-in-apple-travel-portal
- http://ciacfug.org/blog/updating-lucee-as-part-of-a-vulnerability-alert-response
- http://packetstormsecurity.com/files/163864/Lucee-Administrator-imgProcess.cfm-Arbitrary-File-Write.html
- https://dev.lucee.org/t/lucee-vulnerability-alert-november-2020/7643
- https://github.com/httpvoid/writeups/blob/main/Apple-RCE.md
- https://github.com/lucee/Lucee/commit/6208ab7c44c61d26c79e0b0af10382899f57e1ca
- https://github.com/lucee/Lucee/security/advisories/GHSA-2xvv-723c-8p7r
- https://portswigger.net/daily-swig/security-researchers-earn-50k-after-exposing-critical-flaw-in-apple-travel-portal
