CVE-2026-104083
SmarterMail < Build 9777 Stored Mutation XSS via MathML Foreign Content
- State
- Published
- Severity
- 5.3 Medium
- Published
- Oct 9, 2026
- Updated
- Oct 27, 2026
- Reserved
- Oct 1, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 5.3 Medium | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N | VulnCheck |
| 3.1 | 6.1 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N | VulnCheck |
Weaknesses
- CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Products
| Product | Versions |
|---|---|
SmartermailSmartertools |
|
References
- Release Notesrelease-notespatch
- Researcher Blogtechnical-descriptionexploit
- VulnCheck Advisory: SmarterMail < Build 9777 Stored Mutation XSS via MathML Foreign Contentthird-party-advisory
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