CVE-2021-23267
📋 TL;DR
This vulnerability allows authenticated developers in Crafter CMS Studio to execute arbitrary operating system commands through FreeMarker static methods. It affects Crafter CMS installations where developers have access to the Studio interface. The attack requires authenticated developer privileges but can lead to full server compromise.
💻 Affected Systems
- Crafter CMS
📦 What is this software?
Crafter Cms by Craftercms
⚠️ Risk & Real-World Impact
Worst Case
Complete server takeover with attacker gaining root/admin privileges, data exfiltration, lateral movement, and persistent backdoor installation.
Likely Case
Authenticated developers with malicious intent or compromised developer accounts executing commands to steal sensitive data, modify content, or disrupt services.
If Mitigated
Limited impact with proper access controls, developer vetting, and network segmentation preventing lateral movement.
🎯 Exploit Status
Exploitation requires authenticated developer access. FreeMarker template injection leads to OS command execution.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Crafter CMS 3.1.18 and later
Vendor Advisory: https://docs.craftercms.org/en/3.1/security/advisory.html#cv-2022051603
Restart Required: Yes
Instructions:
1. Backup your Crafter CMS installation and database. 2. Download Crafter CMS 3.1.18 or later from official sources. 3. Follow upgrade instructions in documentation. 4. Restart Crafter CMS services. 5. Verify upgrade completed successfully.
🔧 Temporary Workarounds
Restrict Developer Access
allTemporarily remove or restrict developer accounts until patching can be completed.
Network Segmentation
allIsolate Crafter Studio instances from sensitive systems and limit outbound connections.
🧯 If You Can't Patch
- Implement strict access controls and audit all developer activities
- Deploy application firewalls to monitor and block suspicious FreeMarker template executions
🔍 How to Verify
Check if Vulnerable:
Check Crafter CMS version. If running 3.1.x before 3.1.18, system is vulnerable.Check Version:
Check Crafter CMS admin interface or deployment logs for version informationVerify Fix Applied:
Verify Crafter CMS version is 3.1.18 or later and test that FreeMarker static method restrictions are in place.📡 Detection & Monitoring
Log Indicators:
- Unusual FreeMarker template executions
- Suspicious OS command patterns in application logs
- Multiple failed authentication attempts followed by successful developer login
Network Indicators:
- Unexpected outbound connections from Crafter CMS server
- Unusual process spawns from application server
SIEM Query:
source="crafter-logs" AND (freemarker OR "static method" OR "ProcessBuilder" OR "Runtime.exec")