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Cross-Site Scripting in MDaemon Email Server Webmail
CVE-2025-3929 is a cross-site scripting vulnerability in MDaemon Email Server version 25.0.1 and earlier. The flaw can be triggered by sending a specially crafted HTML email containing JavaScript embedded in an img tag. When the message is opened in the webmail interface, attacker-supplied script can execute within the context of the victim user's browser session. This is a webmail-focused, message-triggered XSS condition that can be exploited remotely through email content rendered by the vulnerable client.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation allows arbitrary JavaScript execution in the context of the victim's authenticated webmail session. This can enable theft of user data accessible through the webmail interface, including session-context information and mailbox content available to the user, and can support follow-on actions performed as that user within the browser session.
If you can’t patch tonight, do this now.
Until patched, reduce exposure by restricting access to the webmail interface where operationally feasible, filtering or sanitizing inbound HTML email content, and disabling or limiting active content rendering in webmail if such controls are available. Additional defensive measures include isolating administrative and high-value users from routine webmail use and monitoring for suspicious email messages designed to trigger script execution on message open.
Patch, then assume compromise.
Upgrade MDaemon Email Server to a version newer than 25.0.1 that addresses CVE-2025-3929. Apply the vendor-provided fix for the webmail HTML handling issue and ensure all exposed webmail instances are updated promptly.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
7 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.