CVE-2022-25581
📋 TL;DR
Classcms v2.5 and below contains an arbitrary file upload vulnerability in the classupload component. Attackers can upload crafted .txt files to execute arbitrary code on the server. This affects all deployments using vulnerable versions of Classcms.
💻 Affected Systems
- Classcms
📦 What is this software?
Classcms by Classcms
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to execute arbitrary commands, steal data, install malware, or pivot to other systems.
Likely Case
Webshell deployment leading to data theft, defacement, or use as part of a botnet.
If Mitigated
Limited impact with proper file upload restrictions and web application firewalls in place.
🎯 Exploit Status
Exploitation requires access to file upload functionality but is straightforward once obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: No
Instructions:
Upgrade to a version above v2.5 if available, or apply manual security patches to the classupload component.
🔧 Temporary Workarounds
Restrict file upload extensions
allConfigure web server or application to block .txt file uploads through the classupload component.
# Configure in web server (Apache example):
<Location "/class/classupload">
SetEnvIf Request_URI ".*\.txt$" blocktxt
Deny from env=blocktxt
</Location>
Implement file type validation
allAdd server-side validation to check actual file content, not just extensions.
# PHP example for file validation:
$finfo = finfo_open(FILEINFO_MIME_TYPE);
$mime = finfo_file($finfo, $_FILES['file']['tmp_name']);
if (!in_array($mime, ['image/jpeg', 'image/png'])) {
die('Invalid file type');
}
🧯 If You Can't Patch
- Disable the classupload component entirely if not required.
- Implement a Web Application Firewall (WAF) with rules to block malicious file uploads.
🔍 How to Verify
Check if Vulnerable:
Check if running Classcms v2.5 or below and if file upload functionality is accessible.Check Version:
Check CMS configuration files or admin panel for version information.Verify Fix Applied:
Test file upload with .txt extension to confirm it's blocked or properly validated.📡 Detection & Monitoring
Log Indicators:
- Unusual .txt file uploads to classupload endpoint
- POST requests with file uploads to vulnerable paths
- Subsequent execution of uploaded files
Network Indicators:
- HTTP POST requests to /class/classupload with file uploads
- Unusual outbound connections from web server
SIEM Query:
source="web_logs" AND uri="/class/classupload" AND method="POST" AND file_extension=".txt"