# CVE-2026-104083: SmarterMail < Build 9777 Stored Mutation XSS via MathML Foreign Content

> Remote attackers can execute arbitrary scripts in victim webmail sessions via crafted iCal messages, enabling data exfiltration and session hijacking.

- **Severity:** Medium 5.3 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 9 Oct 2026
- **Updated:** 27 Oct 2026
- **Also known as:** GHSA-vvh8-jc22-6q2f

## What is CVE-2026-104083?

CVE-2026-104083 is a medium-severity cross-site scripting vulnerability in Smartertools Smartermail, published on 9 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-104083?


## How do I fix CVE-2026-104083?

No fix has been published for CVE-2026-104083 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-104083 being exploited?

There is no known exploitation of CVE-2026-104083 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-104083 and fix it if it is affected.

What it is: CVE-2026-104083 is a medium-severity cross-site scripting vulnerability in Smartertools Smartermail, published on 9 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-104083 in the wild and no public exploit code.

Affected product: Smartertools Smartermail. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-104083/ (Markdown: https://insights.sbomify.com/CVE-2026-104083/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-104083
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-104083
- OSV: https://osv.dev/vulnerability/CVE-2026-104083

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-104083/
Summaries are generated and may contain mistakes; the official description above is the record.