Nginx memory disclosure with specially crafted HTTP backend responses
Description
A use-after-free memory vulnerability exists in nginx versions prior to 1.0.14 and versions 1.1.x prior to 1.1.17. When nginx acts as a reverse proxy, a malicious backend HTTP server can send specially crafted responses that trigger improper memory handling. This allows the backend server to read sensitive data from nginx's process memory when processing client requests, potentially exposing confidential information such as session tokens, authentication credentials, or data from other users.
Remediation
Apply the following remediation steps immediately:
1. Upgrade nginx to a patched version:
• For the 1.0.x branch: upgrade to version 1.0.14 or later
• For the 1.1.x branch: upgrade to version 1.1.17 or later
• For production environments: upgrade to the latest stable release
2. Verify the installed version:
nginx -v
3. If immediate patching is not possible, implement these temporary mitigations:
• Restrict backend server connections to trusted hosts only using firewall rules or nginx configuration
• Monitor backend server responses for anomalies
• Review and validate all upstream server configurations
4. After upgrading, restart the nginx service:
sudo systemctl restart nginx
5. Verify proper operation and review logs for any exploitation attempts