Introduction to fxos-k9-kickstart.5.0.3.N2.4.31.202.SPA Software
This Cisco Secure Software Package (SSP) contains the Kickstart bootloader component for Firepower eXtensible OS (FXOS) version 5.0.3.N2.4.31.202, released in Q2 2025 to address critical vulnerabilities in hardware initialization protocols and enhance secure boot validation workflows. Designed for Firepower 4100/9300 series security appliances, this firmware package ensures cryptographic verification of hardware signatures during chassis startup sequences.
The Kickstart image works with FXOS infrastructure bundles (minimum v5.0.3) to validate platform components before loading the full operating system. This build specifically resolves 6 CVEs detailed in Cisco Security Advisory cisco-sa-2025-fxos-bootsec-DEF456, including a high-severity UEFI firmware bypass vulnerability (CVE-2025-14901).
Key Features and Improvements
1. Enhanced Secure Boot Protections
- Patched CVE-2025-14901: Secure Boot bypass via unsigned PCIe device initialization (CVSS 9.1)
- Fixed CSCvp88542: Improper RAID controller signature validation during cold boot
- Added FIPS 140-3 compliant cryptographic module for hardware attestation
2. Platform Initialization Optimization
- 35% faster POST sequence compared to FXOS 5.0.2 kickstart images
- Improved error handling for NVMe storage device detection failures
- Extended hardware support for Firepower 4145/4155 EoL models
3. Diagnostic & Recovery Enhancements
- Resolved false-positive temperature alerts during hardware initialization
- Added detailed boot failure logs accessible via CIMC CLI diagnostics
- Improved compatibility with third-party 100G network modules
Compatibility and Requirements
Supported Hardware Platforms
| Appliance Series | Supported Models | Minimum FXOS Version |
|---|---|---|
| Firepower 4100 | 4110/4125/4140/4145 | 2.17(1.208) |
| Firepower 9300 | 9324/9356/9396 | 3.14(2.105) |
Software Dependencies
- Firepower Management Center 7.4.2 or newer
- Cisco Defense Orchestrator 2.22+ for cloud-managed deployments
- ASA 9.20(3) compatibility mode for hybrid security configurations
Known limitations include temporary service interruption (~120 seconds) when upgrading from FXOS 4.x kickstart versions. Cisco recommends sequential upgrades for environments using legacy 40G network modules.
Verified Download Availability
While Cisco typically restricts access to active Smart License holders, our platform at https://www.ioshub.net provides emergency access to this Kickstart image with SHA-512 checksum verification (5c8d3f…b9a42e). Enterprise users should reference Cisco TAC case ID CSCvp88542 when reporting hardware initialization issues.
This article consolidates technical specifications from Cisco FXOS 5.0.3 Release Notes and Secure Boot Configuration Guides. Always verify platform compatibility using Cisco’s Software Checker before deployment.
