CVE-2013-0803
📋 TL;DR
CVE-2013-0803 is a critical file upload vulnerability in PolarBear CMS 2.5 that allows unauthenticated attackers to upload arbitrary PHP files via upload.php, leading to remote code execution. This affects all systems running the vulnerable version of PolarBear CMS. Attackers can gain complete control over affected web servers.
💻 Affected Systems
- PolarBear CMS
📦 What is this software?
Polarbear Cms by Polarbear Cms Project
⚠️ Risk & Real-World Impact
Worst Case
Complete server compromise allowing attackers to execute arbitrary commands, steal data, install backdoors, pivot to internal networks, and maintain persistent access.
Likely Case
Webshell deployment leading to data exfiltration, website defacement, and use of compromised server for further attacks.
If Mitigated
No impact if proper file upload validation, file type restrictions, and web application firewalls are implemented.
🎯 Exploit Status
Multiple public exploits available since 2013, trivial to exploit with basic HTTP requests.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown - PolarBear CMS appears abandoned
Vendor Advisory: None available
Restart Required: No
Instructions:
1. Upgrade to a different, maintained CMS platform. 2. If continuing with PolarBear CMS, manually implement file upload validation in upload.php. 3. Remove or restrict access to upload.php if not needed.
🔧 Temporary Workarounds
Disable upload.php
linuxRemove or rename the vulnerable upload.php file
mv /path/to/polarbear/upload.php /path/to/polarbear/upload.php.disabled
chmod 000 /path/to/polarbear/upload.php.disabled
Implement file upload validation
allAdd PHP code to validate file types and extensions before processing uploads
Edit upload.php to add: $allowed_extensions = array('jpg', 'png', 'gif'); $file_extension = strtolower(pathinfo($_FILES['file']['name'], PATHINFO_EXTENSION)); if(!in_array($file_extension, $allowed_extensions)) { die('Invalid file type'); }
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block PHP file uploads to upload.php
- Restrict network access to the CMS admin interface and upload functionality
🔍 How to Verify
Check if Vulnerable:
Check if upload.php exists in PolarBear CMS directory and test uploading a PHP file with simple content like <?php echo 'test'; ?>Check Version:
Check CMS version in admin panel or look for version markers in source filesVerify Fix Applied:
Attempt to upload a PHP file - should be rejected. Verify upload.php is disabled or properly validates file types.📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to upload.php with .php files
- Unusual file creations in upload directories
- Webshell access patterns
Network Indicators:
- POST requests to /upload.php with PHP content
- Unexpected outbound connections from web server
SIEM Query:
source="web_logs" AND uri="/upload.php" AND method="POST" AND (file_extension="php" OR content_type="application/x-php")🔗 References
- http://www.exploit-db.com/exploits/24549
- https://exchange.xforce.ibmcloud.com/vulnerabilities/82378
- https://packetstormsecurity.com/files/cve/CVE-2013-0803
- http://www.exploit-db.com/exploits/24549
- https://exchange.xforce.ibmcloud.com/vulnerabilities/82378
- https://packetstormsecurity.com/files/cve/CVE-2013-0803
