CVE-2013-10051
📋 TL;DR
This CVE describes a critical remote code execution vulnerability in InstantCMS versions 1.6 and earlier. Attackers can execute arbitrary PHP code on affected systems by sending specially crafted HTTP requests containing base64-encoded payloads. Any organization running vulnerable InstantCMS installations is at risk of complete system compromise.
💻 Affected Systems
- InstantCMS
📦 What is this software?
Instantcms by Instantcms
⚠️ Risk & Real-World Impact
Worst Case
Complete server takeover, data theft, ransomware deployment, and lateral movement to other systems in the network.
Likely Case
Webshell installation leading to data exfiltration, defacement, or use as a pivot point for further attacks.
If Mitigated
Attack blocked at WAF level or system isolated before exploitation.
🎯 Exploit Status
Metasploit module available. Exploitation requires only HTTP GET requests with crafted parameters.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 1.6
Vendor Advisory: https://instantcms.ru/
Restart Required: No
Instructions:
1. Upgrade to InstantCMS version after 1.6. 2. Replace vulnerable search.php file with patched version. 3. Remove any eval() calls that process user input.
🔧 Temporary Workarounds
WAF Rule Implementation
allBlock requests containing base64-encoded payloads in Cmd headers or look parameters
# Example ModSecurity rule: SecRule ARGS:look "@rx [A-Za-z0-9+/]{50,}=" "id:100051,phase:2,deny,status:403,msg:'CVE-2013-10051 InstantCMS RCE attempt'"
# Example nginx rule: if ($arg_look ~* "[A-Za-z0-9+/]{50,}=") { return 403; }
File Access Restriction
linuxRestrict access to vulnerable search.php file
# Apache .htaccess: <Files "search.php"> Order Deny,Allow Deny from all </Files>
# nginx: location ~* /search\.php$ { deny all; }
🧯 If You Can't Patch
- Immediately isolate affected systems from network access
- Implement strict network segmentation and monitor for suspicious outbound connections
🔍 How to Verify
Check if Vulnerable:
Check InstantCMS version in admin panel or examine /includes/version.php file. If version <= 1.6, system is vulnerable.Check Version:
grep -r "define('VERSION'" /path/to/instantcms/ || cat /path/to/instantcms/includes/version.phpVerify Fix Applied:
Verify version > 1.6 and search for 'eval(' in search-related PHP files. No eval() calls should process user input.📡 Detection & Monitoring
Log Indicators:
- HTTP GET requests to search.php with look parameter containing base64 strings
- Unusual PHP processes spawned from web server user
- Webshell creation in web-accessible directories
Network Indicators:
- Base64-encoded payloads in HTTP headers or parameters
- Unusual outbound connections from web server
SIEM Query:
source="web_logs" AND (uri="*search.php*" AND (param="*look=*" OR header="*Cmd:*")) AND (content="*[A-Za-z0-9+/]{50,}=*" OR content="*base64_decode*" OR content="*eval(*")🔗 References
- https://packetstorm.news/files/id/122176
- https://raw.githubusercontent.com/rapid7/metasploit-framework/master/modules/exploits/unix/webapp/instantcms_exec.rb
- https://www.exploit-db.com/exploits/26622
- https://www.vulncheck.com/advisories/instantcms-remote-php-code-execution
- https://www.exploit-db.com/exploits/26622
