---
id: CVE-2025-34404
title: "MailEnable versions prior to 10.54 contain\_a reflected cross-site scripting (XSS) vulnerability in the InstanceScope parameter of /Mondo/lang/sys/Forms/CAL/compose.aspx"
summary: "MailEnable versions prior to 10.54 contain\_a reflected cross-site scripting (XSS) vulnerability in the InstanceScope parameter of /Mondo/lang/sys/Forms/CAL/compose.aspx. The InstanceScope value is not properly sanitized when processed vi…"
severity: medium
cvss: 6.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'
cwe:
  - CWE-79
vendor: mailenable
product: mailenable
affected:
  - mailenable < 10.54
patched:
  - mailenable 10.54
published: '2025-12-09'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T21:10:00.183'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-34404'
references:
  - url: 'https://mailenable.com/Standard-ReleaseNotes.txt'
    label: disclosure@vulncheck.com
  - url: 'https://www.mailenable.com/'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/mailenable-reflected-xss-in-instancescope-parameter-of-cal-compose-aspx
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.00395
epssPercentile: 0.31972
ingestedAt: '2026-10-14T21:57:04.754Z'
---

## Overview

MailEnable versions prior to 10.54 contain a reflected cross-site scripting (XSS) vulnerability in the InstanceScope parameter of /Mondo/lang/sys/Forms/CAL/compose.aspx. The InstanceScope value is not properly sanitized when processed via a GET request and is reflected inside a <script> block in the JavaScript variable var gInstanceScope. By supplying a crafted payload that terminates the existing PageLoad() function, inserts attacker-controlled script, and comments out remaining code, a remote attacker can execute arbitrary JavaScript in a victim’s browser. Successful exploitation can redirect victims to malicious sites, steal non-HttpOnly cookies, inject arbitrary HTML or CSS, and perform actions as the authenticated user.

## Affected

- `mailenable < 10.54`

## Remediation

Upgrade past the affected range:

- `mailenable 10.54`