CVE-2021-42228
📋 TL;DR
This CSRF vulnerability in KindEditor 4.1.x allows attackers to trick authenticated users into performing unintended file uploads via malicious requests. It affects web applications using the vulnerable KindEditor component, particularly those with file upload functionality enabled. The vulnerability is exploitable when users are logged into affected systems.
💻 Affected Systems
- KindEditor
📦 What is this software?
Kindeditor by Kindsoft
⚠️ Risk & Real-World Impact
Worst Case
Attackers could upload malicious files (webshells, malware) to the server, potentially leading to complete system compromise and data exfiltration.
Likely Case
Unauthorized file uploads leading to defacement, malware distribution, or limited server access depending on file permissions.
If Mitigated
With proper CSRF protections, the vulnerability cannot be exploited even if the vulnerable component remains present.
🎯 Exploit Status
CSRF attacks require user interaction (visiting malicious page while authenticated) but are well-documented and easy to implement.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.1.13 and later
Vendor Advisory: https://github.com/kindsoft/kindeditor/issues/337
Restart Required: No
Instructions:
1. Update KindEditor to version 4.1.13 or later. 2. Replace the vulnerable uploadbutton.html file. 3. Verify CSRF tokens are properly implemented in all file upload endpoints.
🔧 Temporary Workarounds
Disable file upload functionality
allRemove or disable the vulnerable uploadbutton.html example and any file upload features in KindEditor configuration.
Remove examples/uploadbutton.html from your KindEditor installation
Implement CSRF protection
allAdd CSRF tokens to all file upload forms and validate them server-side.
🧯 If You Can't Patch
- Implement strict file type validation and size limits on uploads
- Store uploaded files outside web root with restricted permissions
🔍 How to Verify
Check if Vulnerable:
Check if KindEditor version is 4.1.x and if examples/uploadbutton.html exists without CSRF protection.Check Version:
Check KindEditor source files for version information or examine package.json if available.Verify Fix Applied:
Verify KindEditor version is 4.1.13+ and test that file uploads require valid CSRF tokens.📡 Detection & Monitoring
Log Indicators:
- Unexpected file uploads to KindEditor endpoints
- File uploads without proper referrer/CSRF validation
Network Indicators:
- POST requests to upload endpoints without CSRF tokens
- Requests from unexpected origins to upload endpoints
SIEM Query:
source="web_server" AND (uri="/kindeditor/upload*" OR uri="*/uploadbutton.html") AND NOT csrf_token=*