CVE-2021-41024
📋 TL;DR
This vulnerability allows unauthenticated attackers to perform path traversal attacks on FortiOS and FortiProxy login pages, potentially exposing sensitive server information. Attackers can inject path traversal sequences in GET requests to access files outside intended directories. Affected systems include FortiOS 7.0.0-7.0.1 and FortiProxy 7.0.0.
💻 Affected Systems
- FortiOS
- FortiProxy
📦 What is this software?
Fortios by Fortinet
Fortios by Fortinet
Fortiproxy by Fortinet
⚠️ Risk & Real-World Impact
Worst Case
Complete server file system disclosure including configuration files, credentials, and sensitive system information leading to full system compromise.
Likely Case
Partial information disclosure of web-accessible files, potentially revealing configuration details that could enable further attacks.
If Mitigated
Limited or no information disclosure due to proper input validation and access controls.
🎯 Exploit Status
Simple HTTP GET request manipulation required, no authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FortiOS 7.0.2+, FortiProxy 7.0.1+
Vendor Advisory: https://fortiguard.com/advisory/FG-IR-21-181
Restart Required: Yes
Instructions:
1. Backup current configuration. 2. Download and install FortiOS 7.0.2+ or FortiProxy 7.0.1+ from Fortinet support portal. 3. Apply firmware update via web interface or CLI. 4. Reboot device. 5. Verify version update.
🔧 Temporary Workarounds
Restrict Web Interface Access
allLimit access to management interface using firewall rules or access controls.
Disable Unnecessary Web Services
allTurn off web management interface if not required for operations.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate affected devices
- Deploy WAF with path traversal protection rules
🔍 How to Verify
Check if Vulnerable:
Check FortiOS/FortiProxy version via web interface or CLI 'get system status' command.Check Version:
get system status | grep VersionVerify Fix Applied:
Verify version is FortiOS 7.0.2+ or FortiProxy 7.0.1+ and test path traversal attempts return proper errors.📡 Detection & Monitoring
Log Indicators:
- HTTP GET requests with ../ sequences to login page
- Unusual file access patterns in web logs
Network Indicators:
- HTTP requests containing path traversal patterns to management interface
SIEM Query:
source="fortigate" AND (url="*../*" OR url="*..\\*" OR url="*%2e%2e%2f*") AND uri_path="/login*"