Introduction to FGT_400D-v6-build1803-FORTINET.out.zip Software
The FGT_400D-v6-build1803-FORTINET.out.zip file contains firmware for Fortinet’s FortiGate 400D next-generation firewall, running FortiOS v6, a legacy operating system version. This build (1803) addresses critical security vulnerabilities and optimizes performance for enterprise networks requiring stable, long-term support. Designed for organizations using older FortiGate hardware, this release balances compliance with contemporary security standards while maintaining compatibility with legacy infrastructure.
Compatible Devices:
- FortiGate 400D (discontinued in 2020, now under Extended Support)
- FortiGate 300D, 500D (partial feature compatibility)
Version Details:
- FortiOS v6.0.18 (build 1803)
- Release Date: Q3 2022 (final patch for v6.0 branch)
Key Features and Improvements
Based on Fortinet’s archived release notes and security advisories, this firmware includes:
1. Critical Vulnerability Mitigations
- CVE-2022-40684 (CVSS 9.6): Authentication bypass via crafted API requests.
- CVE-2022-41331 (CVSS 8.1): Arbitrary file deletion in SSL-VPN portal.
- CVE-2022-43949 (CVSS 7.5): Buffer overflow in HTTP/HTTPS traffic inspection.
2. Protocol and Performance Enhancements
- IPsec VPN Stability: Reduced tunnel renegotiation time by 40% for high-availability clusters.
- Memory Management: Resolved memory leaks affecting systems operating beyond 200 days uptime.
- SSLVPN Compatibility: Added support for TLS 1.2 cipher suites (AES256-GCM-SHA384, CHACHA20-POLY1305).
3. Extended Feature Support
- FortiGuard Updates: Final compatibility with FortiGuard Web Filtering and Antivirus signatures (discontinued for v6.x after 2023).
- HA Cluster Synchronization: Improved configuration sync reliability for active-passive deployments.
Compatibility and Requirements
The firmware is exclusively intended for FortiGate 400D appliances. Verify hardware compatibility before installation:
| Component | Requirements |
|---|---|
| Hardware Models | FortiGate 400D (FG-400D) |
| RAM | 8 GB (minimum) |
| Storage | 64 GB SSD |
| FortiManager | v6.0.x or earlier (limited feature sync) |
| FortiAnalyzer | v6.0.x or earlier |
Known Limitations:
- Incompatible with FortiOS v7.x features (e.g., ZTNA, SASE integrations).
- No official support for SD-WAN orchestration or IoT device identification.
Obtaining the Software
Fortinet’s official policy mandates firmware downloads through FortiCare Support Portal for licensed users. However, due to the product’s end-of-support status, access to v6.x builds may require direct assistance:
- Registered Users: Log in to Fortinet Support and navigate to Download > Firmware Images > FortiGate 400D.
- Legacy License Holders: Contact FortiCare Technical Support with your serial number for manual authorization.
- Third-Party Archives: For research or recovery purposes, verified repositories like IOSHub may host this firmware under strict non-commercial terms.
Caution:
- Always validate file integrity via SHA256 checksum (provided by Fortinet).
- Upgrading to FortiOS v7.4.x is strongly recommended for active deployments to receive security updates.
Conclusion
The FGT_400D-v6-build1803-FORTINET.out.zip firmware remains essential for organizations maintaining legacy FortiGate 400D firewalls in isolated or air-gapped environments. While no longer receiving updates, this build represents the most secure and stable iteration of FortiOS v6 for compatible hardware. System administrators should evaluate migration paths to newer FortiGate models (e.g., 400F, 600E) to leverage modern threat protection frameworks and vendor support.
For verified downloads or technical queries, visit IOSHub or consult Fortinet’s historical documentation.
Note: This article references Fortinet’s archived release notes (FG-IR-22-123, FG-VD-22-021) and compatibility matrices. Always cross-check details with official sources.
