Introduction to fxos-k9-kickstart.5.0.3.N2.4.120.776.SPA
This critical infrastructure bundle provides the foundational firmware for Cisco Firepower 4100 Series and 9300 Series appliances running FXOS (Firepower Extensible Operating System) 5.0.3. The “N2.4.120.776” build integrates 28 security patches and platform stability improvements validated through Cisco’s extended lifecycle testing program.
Designed for chassis management and hardware abstraction, this kickstart image enables secure boot operations and serves as the baseline for subsequent security service processor (SSP) updates. Cisco’s technical documentation confirms backward compatibility with FXOS 5.0.x environments while requiring hardware reinitialization for systems running legacy 4.x firmware.
Key Features and Improvements
1. Enhanced Platform Security
- Addresses CVE-2025-20199: Patches privilege escalation vulnerability in CLI command parsing
- Implements FIPS 140-3 compliant cryptographic modules for management plane communications
- Strengthens secure boot validation through SHA-384 certificate chain verification
2. Hardware Compatibility Expansion
- Adds support for 4th Gen Intel Xeon Scalable processors in Firepower 9300-96S models
- Improves PCIe 5.0 device recognition for 100GbE QSFP28 network modules
3. Operational Reliability
- Reduces firmware update downtime by 35% through parallel flash programming
- Fixes false positive HDD failure alerts on Firepower 4112/4120 appliances
- Enhances environmental monitoring with precision voltage regulation (±1%)
Compatibility and Requirements
| Supported Hardware | Minimum FXOS Version | Required Bootloader |
|---|---|---|
| Firepower 4112 | 4.2.5.110 | U-Boot 2022.04 |
| Firepower 4120 | 4.3.1.205 | U-Boot 2022.07 |
| Firepower 9300 | 4.1.9.77 | U-Boot 2021.12 |
Prerequisites:
- 64GB USB 3.2 installation media (FAT32 formatted)
- Disabled Secure Boot for systems previously running FXOS <5.0.0
Incompatible Components:
- Cisco Catalyst 9400 Series Supervisor Engines
- Legacy Firepower 8000 Series SSP modules
Secure Distribution and Verification
This platform bundle requires active Cisco service contracts for authenticated access via the Cisco Software Center. Third-party redistribution violates Cisco’s End User License Agreement and may expose networks to tampered binaries.
Administrators can verify package integrity through https://www.ioshub.net‘s TLS 1.3 encrypted portal, which maintains cryptographic parity with Cisco’s original distribution channels. The platform provides:
Validation Parameters:
- File Size: 683.4 MB
- SHA-512: 9b2a…fd7c
- Cisco Digital Signature: Valid until 2027-12-31
Always cross-reference these values with Cisco’s Security Advisory Hub before deployment.
This technical bulletin consolidates information from Cisco’s FXOS 5.0.3 release documentation. Confirm hardware-specific requirements through Cisco’s Compatibility Matrix prior to installation.
