CVE-2020-28246
📋 TL;DR
This CVE describes a Server-Side Template Injection vulnerability in Form.io version 2.0.0 that allows remote code execution when deleting the default email template URL. The vulnerability affects systems running Form.io 2.0.0 with email templating enabled. The vendor disputes the severity, claiming the feature is sandboxed and only accessible to administrators.
💻 Affected Systems
- Form.io
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining complete control over the server, allowing data theft, lateral movement, and persistent access.
Likely Case
Administrative account compromise leading to unauthorized access to form data, configuration changes, and potential data exfiltration.
If Mitigated
Limited impact due to proper access controls and monitoring, with only authorized administrative actions being possible.
🎯 Exploit Status
Exploitation requires administrative access to the email template deletion functionality. No public exploit code is available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 2.0.0
Vendor Advisory: https://github.com/formio/enterprise-release/blob/master/API-Server-Change-Log.md
Restart Required: Yes
Instructions:
1. Upgrade Form.io to version after 2.0.0. 2. Remove email templating feature entirely. 3. Restart the application server.
🔧 Temporary Workarounds
Disable Email Templating
allCompletely disable the email templating feature to remove the attack surface
Modify configuration to disable email template functionality
Restrict Administrative Access
allImplement strict access controls to limit who can access template management functions
Configure role-based access control to restrict template operations to minimum necessary users
🧯 If You Can't Patch
- Implement network segmentation to isolate Form.io servers from critical systems
- Enable detailed logging and monitoring of all template-related operations
🔍 How to Verify
Check if Vulnerable:
Check if running Form.io version 2.0.0 with email templating enabledCheck Version:
Check package.json or application configuration for Form.io versionVerify Fix Applied:
Verify Form.io version is after 2.0.0 and email templating is disabled📡 Detection & Monitoring
Log Indicators:
- Unusual template deletion operations
- Multiple failed template access attempts
- Administrative actions from unexpected IP addresses
Network Indicators:
- Unusual outbound connections from Form.io server
- HTTP requests to template deletion endpoints
SIEM Query:
source="formio" AND (event="template_delete" OR event="email_template")