Sagnik Ghosh
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Writeups and notes.

CTF writeups, lab walkthroughs and the occasional security note, dead ends included.

Carribean: Spectronas CTF 2026 B2R The Caribbean B2R machine involves anonymous FTP enumeration, steganography, web directory discovery, cookie manipulation, and file upload exploitation to gain a shell. SSH keys recovered from an encrypted ZIP provide user access. Privilege escalation is achieved through a tar wildcard injection vulnerability in a custom backup script, leading to root access and the final flag. CTFWalkthroughboot2rootSpectronas CTF 2026 8 min read → Amongus: Spectronas CTF 2026 B2R A complete walkthrough of the Amongus B2R machine, covering SMB and FTP enumeration, virtual host discovery, PHP Local File Inclusion (LFI), writable NFS exploitation for initial access, SSH credential discovery, and privilege escalation to root using PwnKit (CVE-2021-4034). CTFWalkthroughboot2rootSpectronas CTF 2026 18 min read → Nexus: HTB Walkthrough A penetration test of the Nexus HTB machine, covering port scanning, virtual host enumeration, credential discovery through a Gitea instance, and initial access via a vulnerable Krayin CRM installation. Privilege escalation to root was achieved by exploiting a path traversal weakness in a root-owned Gitea template synchronization service, allowing an SSH public key to be written to root's `authorized_keys` file. HTBWalkthroughboot2root 14 min read → Implementing Repeating-key XOR cipher Implementing a repeating-key XOR cipher in Python: a Cryptopals Set 1 Challenge 5 writeup covering XOR basics, strings and a full implementation. CryptographyCTFsXORCryptopals 2 min read → Basic Pentesting 1 Walkthrough Basic Pentesting 1 boot2root walkthrough: Nmap recon, exploiting a vulnerable FTP service with Metasploit, and web enumeration with Gobuster. Privilege EscalationMetasploitboot2root 4 min read → Blue TryHackMe Walkthrough TryHackMe Blue walkthrough: scanning a Windows 7 host with Nmap, confirming MS17-010 (EternalBlue) and gaining a Meterpreter session with Metasploit. NetworkMetasploitSMB 5 min read → NetSec Challenge TryHackMe Walkthrough TryHackMe NetSec Challenge walkthrough: using Nmap to find open ports, service versions and hidden services on a target host. NetworkReconnaissance 4 min read →