CVE-2021-41729
📋 TL;DR
BaiCloud-cms v2.5.7 has an arbitrary file deletion vulnerability in /user/ppsave.php, allowing attackers to delete any files on the server. This affects users running the vulnerable version of BaiCloud-cms, potentially leading to data loss or system disruption.
💻 Affected Systems
- BaiCloud-cms
📦 What is this software?
Baicloud Cms by Baicloud Cms Project
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise or data destruction, including deletion of critical system files, causing service outages or permanent data loss.
Likely Case
Deletion of web application files, configuration files, or user data, leading to application downtime or data corruption.
If Mitigated
Limited impact if file permissions are restrictive or the vulnerability is blocked by network controls, but still poses a risk to exposed files.
🎯 Exploit Status
Exploitation is straightforward as it involves sending crafted requests to the vulnerable endpoint without authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
No official patch is available; consider upgrading to a newer version if released or applying workarounds.
🔧 Temporary Workarounds
Block access to vulnerable endpoint
allRestrict access to /user/ppsave.php using web server configuration or firewall rules to prevent exploitation.
For Apache: add 'Deny from all' in .htaccess for /user/ppsave.php
For Nginx: add 'location /user/ppsave.php { deny all; }' in server block
Remove vulnerable file
linuxDelete or rename the /user/ppsave.php file to eliminate the attack vector, but ensure it does not break application functionality.
rm /path/to/BaiCloud-cms/user/ppsave.php
mv /path/to/BaiCloud-cms/user/ppsave.php /path/to/BaiCloud-cms/user/ppsave.php.bak
🧯 If You Can't Patch
- Implement strict file permissions to limit write/delete access to critical directories.
- Monitor and log access to /user/ppsave.php for suspicious activity and set up alerts.
🔍 How to Verify
Check if Vulnerable:
Check if BaiCloud-cms version is 2.5.7 and if /user/ppsave.php exists and is accessible via HTTP requests.Check Version:
Check the CMS version in the application's admin panel or configuration files; no standard command available.Verify Fix Applied:
Verify that /user/ppsave.php is no longer accessible or has been removed, and test with controlled requests to confirm deletion attempts fail.📡 Detection & Monitoring
Log Indicators:
- HTTP requests to /user/ppsave.php with parameters indicating file deletion attempts
- Unusual file deletion events in system or application logs
Network Indicators:
- Inbound traffic to /user/ppsave.php endpoint with suspicious payloads
SIEM Query:
Example: 'source="web_logs" AND url="/user/ppsave.php" AND (method="POST" OR method="GET")'