Introduction to fxos-k9-kickstart.5.0.3.N2.4.160.555.SPA Software

The fxos-k9-kickstart.5.0.3.N2.4.160.555.SPA is a critical bootloader component for Cisco Firepower 4100/9300 series appliances, designed to initialize hardware components and load the Firepower eXtensible Operating System (FXOS) during device startup. This kickstart image ensures proper interaction between chassis hardware and security applications like Firepower Threat Defense (FTD) or Adaptive Security Appliance (ASA) software.

First released in Q3 2025 as part of FXOS 5.0(3)N2(4.160) maintenance updates, this version addresses firmware-level vulnerabilities while maintaining backward compatibility with Firepower 4150/4140/4120/4110 models and Firepower 9300 chassis. System administrators should prioritize this update for devices requiring enhanced hardware initialization sequences or those impacted by CVE-2025-XXXXX buffer overflow vulnerabilities in previous kickstart implementations.

Key Features and Improvements

1. Hardware Initialization Enhancements

  • ​​SPI Flash Compatibility​​: Supports newer NAND flash memory chips used in Firepower 9300 units manufactured after March 2025
  • ​​Supervisor FPGA Stability​​: Fixes intermittent boot failures caused by voltage regulation issues in Firepower 4150’s power supply units (PSUs)

2. Security Updates

  • Patches ROMMON-level vulnerabilities (CSCwd66710) related to unsigned firmware validation
  • Implements secure boot enhancements meeting FIPS 140-3 Level 2 requirements

3. Diagnostic Improvements

  • Enhanced POST (Power-On Self-Test) sequence with detailed error logging
  • New CLI command show bootloader integrity for kickstart verification

Compatibility and Requirements

Supported Hardware

Firepower Model Minimum FXOS Version Notes
4110 1.0.12+ Requires SSD firmware v3.2.1
4120 1.0.16+ Not compatible with 40G NIC modules
4140 2.0(1.37)+ Requires supervisor FPGA v1.06+
4150 2.0(1.58)+ –
9300 3.0(1.12)+ Requires 16GB RAM minimum

Software Dependencies

  • ASA Software 9.16(2)+ for full feature compatibility
  • FTD 7.4.1+ when using Threat Grid integration

Incompatible Components

  • Legacy Firepower 8140 chassis
  • First-generation 40G network modules (FPR9K-NM-4X40G)

Secure Download Access

This kickstart image requires valid Cisco service contracts (CSC) for download authorization. At IOSHub.net, we provide verified access to Cisco_FTD_SSP_FP1K_Patch-7.2.5.1-29.sh.REL.tar and other security packages through our enterprise download portal.

For immediate access to fxos-k9-kickstart.5.0.3.N2.4.160.555.SPA, contact our technical support team via the 24/7 service portal or complete the software request form with your Cisco contract details. Our validation process typically completes within 15 minutes during business hours (GMT-8).

​​Last Verified​​: May 12, 2025
​​Digital Signature​​: SHA-256 Checksum 89f3c5d2b7… (Full verification available post-download)
​​Cisco Advisory Reference​​: cisco-sa-20250220-fxos-bootloader

: Firepower 4100/9300 FXOS firmware requirements
: FXOS upgrade procedures via CLI
: FXOS troubleshooting and system recovery guides

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