CVE-2021-45807
📋 TL;DR
CVE-2021-45807 is a critical remote code execution vulnerability in JPress v4.2.0 that allows attackers to execute arbitrary commands on affected systems via the doUploadAndInstall function in the AddonController. This affects all JPress v4.2.0 installations with the vulnerable endpoint accessible. Attackers can gain complete control over the server.
💻 Affected Systems
- JPress
📦 What is this software?
Jpress by Jpress
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to execute arbitrary commands, install malware, exfiltrate data, pivot to internal networks, and maintain persistent access.
Likely Case
Attackers upload malicious addons containing webshells or backdoors, gaining administrative access to the JPress instance and potentially the underlying server.
If Mitigated
With proper network segmentation and access controls, impact is limited to the JPress application container or isolated environment.
🎯 Exploit Status
Exploitation requires admin authentication. The vulnerability is in the addon upload/installation mechanism which can be abused to upload malicious files.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v4.2.1 or later
Vendor Advisory: https://github.com/JPressProjects/jpress/issues/167
Restart Required: Yes
Instructions:
1. Backup your JPress installation and database. 2. Download the latest JPress version from the official repository. 3. Replace the existing installation with the updated version. 4. Restart the JPress application server. 5. Verify the fix by checking the version.
🔧 Temporary Workarounds
Disable Addon Upload
allRemove or restrict access to the vulnerable AddonController endpoint
# Modify web.xml or application configuration to restrict /admin/addon/* endpoints
# Add authentication/authorization checks for addon management functions
Network Access Control
linuxRestrict access to admin interface using firewall rules
# iptables -A INPUT -p tcp --dport [JPress-port] -s [trusted-ips] -j ACCEPT
# iptables -A INPUT -p tcp --dport [JPress-port] -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate JPress from critical systems
- Enable detailed logging and monitoring for addon upload activities and unusual admin actions
🔍 How to Verify
Check if Vulnerable:
Check JPress version in admin dashboard or by examining application files. Version 4.2.0 is vulnerable.Check Version:
# Check JPress version in admin interface or examine WEB-INF/classes/version.properties fileVerify Fix Applied:
Verify version is 4.2.1 or later. Test addon upload functionality with safe test files to ensure proper validation.📡 Detection & Monitoring
Log Indicators:
- Unusual addon upload activities
- Multiple failed addon installation attempts
- Admin login from unusual IP addresses
- Execution of unexpected system commands
Network Indicators:
- HTTP POST requests to /admin/addon/upload
- Unusual outbound connections from JPress server
- Traffic to known malicious IPs or domains
SIEM Query:
source="jpress.log" AND ("doUploadAndInstall" OR "addon/upload") AND status=200