Hack The Box - HTB Nimbus Writeup - Hard - Weekly - June 21th, 2026

June 20, 2026

OS: Linux · Difficulty: Hard · Theme: Cloud / AWS (LocalStack) misconfiguration Target Attacker (tun0) /etc/hosts nimbus.htb aws.nimbus.htb 0. Setup & the MTU black-hole (do this first) On the HTB VPN, tun0 defaults to MTU 1500 but the real path MTU to the target is ~1300. Oversized packets are silently dropped (no ICMP frag-needed), so small requests succeed while large ones hang forever. On the first solve a ~2.5 KB SQS send-message hung indefinitely while a tiny test went through instantly — pure MTU. Fix it up front so it never bites: sudo ip link set dev tun0 mtu 1300 Con…