XSS in Mailenable
CVE-2025-34399
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (31.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 31st percentile — 31.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000
Affected products
- Mailenable — versions 0
Weakness classification (CWE)
References
- mailenable.com/Standard-ReleaseNotes.txt (release-notes, Release Notes, patch)
- www.mailenable.com/ (Product, product)
- www.vulncheck.com/advisories/mailenable-reflected-xss-in-addressescc-parameter-… (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2025-34399?
- CVE-2025-34399 is a medium-severity vulnerability in Mailenable, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2025-12-09.
- How severe is CVE-2025-34399?
- Medium severity. CVSS v3 base score is 6.1 out of 10.