CVE-2020-25494
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary operating system commands on Xinuos (formerly SCO) Openserver systems via shell metacharacters in the outputform or toclevels parameters of the printbook CGI script. Attackers can achieve full system compromise without authentication. Affects Xinuos Openserver v5 and v6 installations with the vulnerable CGI script exposed.
💻 Affected Systems
- Xinuos Openserver
- SCO Openserver
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system takeover: attacker gains root privileges, installs persistent backdoors, exfiltrates sensitive data, and uses the system as a pivot point for lateral movement.
Likely Case
Remote code execution leading to web server compromise, data theft, and potential ransomware deployment.
If Mitigated
Limited impact with proper network segmentation, but still potential for web server compromise if exposed.
🎯 Exploit Status
Simple HTTP request with crafted parameters can trigger command execution. Multiple public exploit scripts exist.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
No official patch available. Apply workarounds immediately. Monitor Xinuos security advisories for updates.
🔧 Temporary Workarounds
Disable or remove vulnerable CGI script
linuxRemove or restrict access to the vulnerable /cgi-bin/printbook script
mv /usr/www/cgi-bin/printbook /usr/www/cgi-bin/printbook.disabled
chmod 000 /usr/www/cgi-bin/printbook.disabled
Implement input validation in web server configuration
allAdd input filtering rules to block shell metacharacters in CGI parameters
# Add to web server config: mod_security rules or input filtering
🧯 If You Can't Patch
- Network segmentation: Isolate affected systems from critical networks and internet
- Implement strict web application firewall rules to block requests containing shell metacharacters
🔍 How to Verify
Check if Vulnerable:
Test by sending HTTP request: curl -X POST 'http://target/cgi-bin/printbook' --data 'outputform=;id;' and check for command outputCheck Version:
uname -a && cat /etc/issueVerify Fix Applied:
Verify script is removed/disabled: ls -la /usr/www/cgi-bin/printbook* and test with same curl command expecting 404 or access denied📡 Detection & Monitoring
Log Indicators:
- Web server logs showing requests to /cgi-bin/printbook with shell metacharacters (;, |, &, $, etc.)
- System logs showing unexpected command execution from web server user
Network Indicators:
- HTTP POST requests to /cgi-bin/printbook with unusual parameter values
- Outbound connections from web server to suspicious IPs
SIEM Query:
source="web_server" AND uri="/cgi-bin/printbook" AND (param="outputform" OR param="toclevels") AND (value="*;*" OR value="*|*" OR value="*`*" OR value="*$(*")🔗 References
- http://packetstormsecurity.com/files/160635/SCO-Openserver-5.0.7-Command-Injection.html
- https://github.com/Ramikan/Vulnerabilities/blob/master/SCO%20Openserver%20OS%20Command%20Injection%20Vulnerability
- http://packetstormsecurity.com/files/160635/SCO-Openserver-5.0.7-Command-Injection.html
- https://github.com/Ramikan/Vulnerabilities/blob/master/SCO%20Openserver%20OS%20Command%20Injection%20Vulnerability
