CVE-2025-34404

MailEnable < 10.54 Reflected XSS in InstanceScope Parameter of CAL/compose.aspx

MEDIUM
6.1
CVSS Score
Published: December 9, 2025 at 06:07 PM UTC
Updated: October 14, 2026 at 09:10 PM UTC
1 product affected across 1 vendorMailenable

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Severity
MEDIUM6.1
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

Description

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

All versionsv < 10.54
Affected range stops below 10.54, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-79

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