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The Needle — HTB Challenge

retleave·Apr 21, 2026·6 min read

The Needle - HTB Challenge

Info

  • Category: Hardware
  • Difficulty: Easy
  • Key Topics: Firmware analysis, binwalk, SquashFS extraction, OpenWrt, hardcoded credentials in init scripts

Abstract

The Needle provides a 16MB firmware binary and a remote telnet service. The task is to analyze the firmware image to discover hardcoded credentials and use them to authenticate to the remote service. The firmware is an ARM Linux kernel with an embedded SquashFS root filesystem, characteristic of OpenWrt/LEDE-based embedded devices. Credential discovery requires navigating the extracted filesystem to find init scripts that configure the telnet daemon with a username and password sourced from a configuration file. This writeup covers the full firmware analysis methodology, from initial identification through filesystem extraction to credential harvesting.

Firmware Identification

Initial Analysis

bash
$ file firmware.bin
firmware.bin: Linux kernel ARM boot executable zImage (big-endian)
The file command identifies this as an ARM Linux kernel in zImage format (compressed kernel image). The big-endian byte order suggests an ARM platform configured in BE mode, though many embedded ARM SoCs can operate in either endianness.

Binwalk Analysis

bash
$ binwalk firmware.bin
DECIMAL       HEXADECIMAL     DESCRIPTION
---------------------------------------------------
0             0x0             Linux kernel ARM boot executable zImage
538952        0x83A48         Squashfs filesystem, little endian, version 4.0,

Content Locked

This challenge is still active on HackTheBox. The full writeup will be available after retirement.