CVE-2025-34399: Mailenable

Medium severity, CVSS 6.1. EPSS: 0.4% chance of exploitation in the next 30 days.

MailEnable versions prior to 10.54 contain a reflected cross-site scripting (XSS) vulnerability in the AddressesCc parameter of /Mondo/lang/sys/Forms/AddressBook.aspx. The AddressesCc value is not properly sanitized when processed via a GET request and is reflected within a <script> block in the JavaScript variable var sAddrCc. By supplying a crafted payload that terminates the existing LoadCurAddresses() function, inserts attacker-controlled script, and comments out remaining code, a remote attacker can execute arbitrary JavaScript in a victim’s browser when the victim attempts to send an email. 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 products

• Mailenable Mailenable: before 10.54 (fixed in 10.54)

Published 2025-12-09. Last modified 2026-06-17.