XSS in Smartertools Smartermail
CVE-2026-104083
SmarterMail before build 9777 contains a stored mutation cross-site scripting vulnerability that allows remote attackers to inject executable script by placing payloads inside a <style> element nested within MathML foreign content (<math><mtext><mglyph>), which the custom HTML sanitizer treats as inert CDATA text but browsers reparse as live markup. Attackers can deliver a crafted calendar (iCal) message containing an <img src=x onerror=...> payload that executes automatically in the recipient's webmail session at /interface/message-iframe when the message is opened, enabling script execution and data exfiltration unconstrained by the interface's permissive Content-Security-Policy.
Vulnerability class: XSS (Cross-Site Scripting)
Published .
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
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- www.smartertools.com/smartermail/release-notes/current (release-notes, patch)
- www.vulncheck.com/advisories/smartermail-build-9777-stored-mutation-xss-via-mat… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-104083?
- CVE-2026-104083 is a medium-severity vulnerability in Smartertools Smartermail, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-10-09.
- How severe is CVE-2026-104083?
- Medium severity. CVSS v3 base score is 6.1 out of 10.