CVE-2025-48476

Executive Summary

CVE-2025-48476 is a critical mass-assignment vulnerability in FreeScout, a free self-hosted help desk and shared mailbox application. The vulnerability resides in the fill() method used when adding and editing user records. An authenticated attacker with the right to edit other users can exploit this flaw to change the password of any user, including administrators, without proper authorization. This allows for privilege escalation and full account takeover. The vulnerability is patched in version 1.8.180.

Supply Chain & Package Security

FreeScout is a PHP application. The vulnerability is in the core application code, not in a third-party package. However, administrators should verify the integrity of their FreeScout installation and ensure they are using the official source from the FreeScout GitHub repository.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) - The vulnerability can be exploited remotely over the network.
• Attack Complexity (AC): Low (L) - No special conditions are required for exploitation.
• Privileges Required (PR): Low (L) - An attacker needs a valid user account with the ability to edit other users.
• User Interaction (UI): None (N) - No user interaction is required.
• Scope (S): Unchanged (U) - The vulnerability does not affect other components.
• Confidentiality (C): High (H) - An attacker can gain access to sensitive data by taking over user accounts.
• Integrity (I): High (H) - An attacker can modify user data, including passwords.
• Availability (A): High (H) - An attacker could potentially lock out legitimate users by changing their passwords.

CVSS Score: 8.8 (High)

Threat Level: Critical. The vulnerability allows for complete account takeover with low privileges.

Deep Dive & Mechanics

The vulnerability is a classic mass-assignment (also known as "autobinding") issue. In FreeScout, the fill() method is used to populate model attributes from user input. The method does not properly validate or whitelist the fields that can be set. When a user with the "edit users" permission submits a request to update a user record, the fill() method accepts all fields from the request, including the password field.

An attacker can craft a request that includes a new password for the target user. Since the fill() method does not check for the absence of the password field, the password is updated without any additional authorization checks. The attacker can then log in using the new password.

The vulnerable code path is in the user update functionality. The fill() method is called with the request data, and the password field is not filtered out before being passed to the model.

Vulnerable vs. Patched Code

Vulnerable Code (Pre-1.8.180):

// In UserController or similar
public function update(Request $request, User $user)
{
    $user->fill($request->all());
    $user->save();
    // ...
}

The $request->all() includes the password field, which is then passed to fill().

Patched Code (1.8.180):

// In UserController or similar
public function update(Request $request, User $user)
{
    $data = $request->except(['password']);
    $user->fill($data);
    $user->save();
    // ...
}

The patched code uses $request->except(['password']) to explicitly remove the password field from the request data before calling fill(). This prevents the mass-assignment vulnerability.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A valid user account with the "edit users" permission.
• The target user's ID (e.g., user ID 2 for an admin).

Exploitation Steps:

1. Identify a target user with higher privileges (e.g., an admin).
2. Craft a malicious request to update the target user's profile, including a new password.
3. Send the request to the FreeScout server.

Example cURL Command:

curl -X POST https://target-freescout.com/users/2 \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -H "Cookie: <your_session_cookie>" \
  -d "first_name=Admin&last_name=User&email=admin@example.com&password=newpassword123"

Expected Outcome: The password for user ID 2 is changed to newpassword123. The attacker can then log in as that user.

Blue Team

Detection Steps:

1. Monitor for unusual user update requests that include a password field.
2. Audit user activity logs for password changes made by non-admin users.
3. Check for multiple failed login attempts followed by a successful login from a different IP address.

Hunting Query (Splunk):

index=main sourcetype=apache_access
| search "/users/*" AND "password="
| table _time, src_ip, user, uri, status

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /users/* endpoints containing the password parameter.
  • Unusual login activity from IP addresses not associated with the legitimate user.
• System IOCs:
  • User accounts with recently changed passwords.
  • Audit logs showing password changes without a corresponding password reset request.
• File IOCs:
  • Modified user records in the database.

Detection Engineering

YARA Rule

rule Detect_FreeScout_Mass_Assignment_CVE_2025_48476 {
    meta:
        description = "Detects attempts to exploit CVE-2025-48476 in FreeScout"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-48476"
    strings:
        $s1 = "fill("
        $s2 = "->all()"
        $s3 = "password"
    condition:
        all of ($s1, $s2, $s3)
}

Sigma Rule

title: FreeScout Mass Assignment Exploitation
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP requests attempting to exploit CVE-2025-48476
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/users/*'
        cs-uri-query|contains: 'password='
    condition: selection
falsepositives:
    - Legitimate password changes by administrators
level: high

Suricata Rule

alert http any any -> any any (msg:"FreeScout Mass Assignment Exploit CVE-2025-48476"; flow:to_server,established; content:"POST"; http_method; content:"/users/"; http_uri; content:"password="; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade FreeScout to version 1.8.180 or later.
2. Review user accounts for any unauthorized password changes.
3. Reset passwords for all users, especially administrators.

Long-Term Mitigations:

1. Implement input validation for all user input.
2. Use whitelisting for mass-assignment operations.
3. Enforce strong password policies and multi-factor authentication.
4. Monitor logs for suspicious activity.

Workarounds (if patching is not immediately possible):

• Disable the "edit users" permission for non-administrator accounts.
• Implement a web application firewall (WAF) rule to block requests containing password in the body for user update endpoints.

Valters IT
DevSecOps & Cyber Threat Intelligence