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.NET
.NET NuGet
Not in CISA KEV
HIGH severity

CVE-2020-9471 — UmbracoCMS.Core

HIGH

CVE-2020-9471 is a high-severity (CVSS 8.8) Unrestricted File Upload vulnerability in UmbracoCMS.Core. 3 public exploit or proof-of-concept references are indexed, so weaponization risk is real. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

Umbraco CMS Authenticated File Upload

Also known asGHSA-h68c-4jh3-cp9j
Published
Updated
Affected
1 pkg
Patched
See advisory
Exploits
3 known
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
2.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs83th percentile — riskier than 83% of all scored CVEsHighest risk
1.78%2.33%2.88%3.44%2.9%2.3%May 26Sep 26Nov 26

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

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
.NETUmbracoCMS.Core

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 Cloud 8.5.3 allows an authenticated file upload (and consequently Remote Code Execution) via the Install Packages functionality.

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
.NETNuGetUmbracoCMS.Coreall versionsNo fix

Affected Products

1 product · 1 configurations
Application
umbraco cmsumbraco
1 version
8.5.3
Exploits & PoCs
3

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Umbraco Cloud 8.5.3 allows an authenticated file upload (and consequentl…

gitlab.comNVDMar 2020

Report on gitlab.com

gitlab.comAwesomePocJun 2020

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Remediation status

    The records we use list no patched version of UmbracoCMS.Core for CVE-2020-9471. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

  3. Mitigate without a patch

    Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.

Frequently Asked Questions

Umbraco Cloud 8.5.3 allows an authenticated file upload (and consequently Remote Code Execution) via the Install Packages functionality.
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CVE-2020-9471: UmbracoCMS.Core RCE (High 8.8)