CVE-2025-59413

Executive Summary

CVE-2025-59413 is a logic flaw vulnerability in CubeCart, an open-source ecommerce platform, affecting versions prior to 6.5.11. The vulnerability resides in the newsletter subscription endpoint, where an attacker can force-unsubscribe any valid subscriber’s email address without their consent by manipulating the force_unsubscribe parameter in a POST request. This allows for unauthorized denial of service against the newsletter system, potentially harming marketing operations and user trust. The vulnerability has a CVSS score of 6.5 (Medium) and is currently unpatched in older versions. No public exploit code or proof-of-concept is available at this time.

Supply Chain & Package Security

CubeCart is a PHP-based ecommerce application. This vulnerability does not directly affect package managers like NPM, PyPI, Go, or Ruby. However, organizations using CubeCart should verify their deployment version and apply the patch immediately.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

The threat level is considered medium due to the low complexity and lack of required privileges, but the impact is limited to unauthorized unsubscription of newsletter recipients.

Deep Dive & Mechanics

The vulnerability exists in the newsletter subscription handling logic. The endpoint responsible for managing subscriptions accepts a force_unsubscribe parameter. When this parameter is set to 1, the application processes the unsubscription request without verifying that the requester is the actual subscriber or has their consent. This allows an attacker to craft a POST request with any valid email address and the force_unsubscribe=1 parameter, causing the system to remove that email from the newsletter list.

The root cause is a missing authorization check (CWE-862) on the unsubscription action. The application should require authentication or a token-based confirmation for unsubscription requests, but it does not.

Vulnerable vs. Patched Code

Vulnerable Code (pre-6.5.11):

// In subscription handler
if (isset($_POST['force_unsubscribe']) && $_POST['force_unsubscribe'] == 1) {
    $email = $_POST['email'];
    $db->delete('newsletter_subscribers', array('email' => $email));
}

Patched Code (6.5.11):

// In subscription handler
if (isset($_POST['force_unsubscribe']) && $_POST['force_unsubscribe'] == 1) {
    // Verify the request is from an authenticated admin or the subscriber themselves
    if (isset($_SESSION['user_id']) || (isset($_POST['token']) && validate_token($_POST['token'], $email))) {
        $email = $_POST['email'];
        $db->delete('newsletter_subscribers', array('email' => $email));
    } else {
        // Log unauthorized attempt
        error_log('Unauthorized unsubscribe attempt for: ' . $email);
    }
}

The patch adds a check for either an authenticated session (admin) or a valid token (subscriber consent).

Exploitation & Lab Setup

Red Team

Prerequisites:

• A target CubeCart instance running version < 6.5.11.
• A valid subscriber email address (can be obtained via enumeration or social engineering).

Exploitation Steps:

1. Identify the newsletter subscription endpoint (e.g., /index.php?_a=newsletter).
2. Send a POST request with the following parameters:
   • email: target@example.com
   • force_unsubscribe: 1
3. The target email will be removed from the subscriber list without any notification.

Example cURL command:

curl -X POST https://target.com/index.php?_a=newsletter \
  -d "email=target@example.com&force_unsubscribe=1"

Blue Team

Detection:

• Monitor for POST requests to the newsletter endpoint with force_unsubscribe=1 parameter.
• Look for multiple unsubscription requests from the same IP address in a short time frame.
• Alert on unsubscription requests that do not originate from the subscriber's known IP or session.

Hunting:

• Review web server logs for unusual patterns in the newsletter endpoint.
• Check for missing referer headers or user-agent strings that indicate automated tools.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /index.php?_a=newsletter containing force_unsubscribe=1.
  • Repeated unsubscription requests for different email addresses from the same source IP.
• Logs:
  • Web server logs showing POST /index.php?_a=newsletter with force_unsubscribe=1.
  • Application logs showing deletion of newsletter subscribers without corresponding authentication.
• File System:
  • No specific file-based IOCs.

Detection Engineering

YARA Rule

rule CVE_2025_59413_CubeCart_Unsubscribe {
    meta:
        description = "Detects exploitation attempts of CVE-2025-59413 in CubeCart"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-59413"
    strings:
        $s1 = "force_unsubscribe=1" ascii wide nocase
        $s2 = "_a=newsletter" ascii wide nocase
    condition:
        all of them
}

Sigma Rule

title: CubeCart Unauthorized Unsubscribe Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects POST requests to CubeCart newsletter endpoint with force_unsubscribe parameter
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '_a=newsletter'
        cs-uri-query|contains: 'force_unsubscribe=1'
    condition: selection
falsepositives:
    - Legitimate admin actions (if patched)
level: medium

Suricata Rule

alert http any any -> any any (
    msg:"CVE-2025-59413 CubeCart Unauthorized Unsubscribe Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"_a=newsletter"; http_uri;
    content:"force_unsubscribe=1"; http_client_body;
    classtype:attempted-dos;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Upgrade CubeCart to version 6.5.11 or later.
2. If immediate upgrade is not possible, implement a Web Application Firewall (WAF) rule to block POST requests containing force_unsubscribe=1 to the newsletter endpoint.
3. Monitor logs for any unauthorized unsubscription attempts.

Long-term Measures:

• Enforce authentication or token-based confirmation for all subscription changes.
• Conduct regular security audits of custom endpoints.
• Implement rate limiting on subscription management endpoints.

Workaround:

• Disable the newsletter subscription feature temporarily until the patch is applied.

Valters IT