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.NET
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Not in CISA KEV
MEDIUM severity

CVE-2026-46609 — Umbraco.Cms

MEDIUM

CVE-2026-46609 is a medium-severity (CVSS 4.6) Cross-site Scripting (XSS) vulnerability in Umbraco.Cms. A fix is available for Umbraco.Cms — see the affected versions and patch details below.

Umbraco.Cms: XSS/HTML Injection in Umbraco Backoffice confirmation dialog

Also known asGHSA-vr9v-27gg-qgx4
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 1, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-46609.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk+0.09%
Lower risk than most CVEs13th percentile — riskier than 13% of all scored CVEsHighest risk
0.00%0.24%0.49%0.73%0.1%0.1%0.1%0.2%Jul 26Sep 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-46609 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 382,205 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
.NETUmbraco.Cms

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetUmbraco.Cms≥ 14.0.0&&< 17.4.017.4.0dotnet add package Umbraco.Cms --version 17.4.0

Affected Products

1 product · 1 configurations
Application
umbraco cmsumbraco
≥ 14.0.0 && < 17.4.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Umbraco.Cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update Umbraco.Cms to 17.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-46609 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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CVE-2026-46609: Fixed in 17.4.0 (Medium 4.6) | O3 Security