How severe is GHSA-fr6r-p8hv-x3c4?

GHSA-fr6r-p8hv-x3c4 has a CVSS score of 5.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-fr6r-p8hv-x3c4?

GHSA-fr6r-p8hv-x3c4 affects the following packages: Umbraco.Cms (NuGet). Ecosystems affected: NuGet.

How do I fix GHSA-fr6r-p8hv-x3c4?

Update Umbraco.Cms to 15.4.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fr6r-p8hv-x3c4 is resolved across your whole dependency graph.

How do I detect GHSA-fr6r-p8hv-x3c4 in my NuGet dependencies?

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.

How do I mitigate GHSA-fr6r-p8hv-x3c4 if there is no patch (or I can't update yet)?

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.

Is GHSA-fr6r-p8hv-x3c4 actively exploited in the wild?

No public exploit code has been indexed for GHSA-fr6r-p8hv-x3c4 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-fr6r-p8hv-x3c4?

GHSA-fr6r-p8hv-x3c4 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 9th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-fr6r-p8hv-x3c4?

GHSA-fr6r-p8hv-x3c4 is classified as Unrestricted File Upload (CWE-434). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-fr6r-p8hv-x3c4 published, and has it been updated?

GHSA-fr6r-p8hv-x3c4 was published on June 4, 2025 and was last updated on June 5, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

.NET

.NET NuGet

Not in CISA KEV

MEDIUM severity

Umbraco Vulnerable to By-Pass of Configured Allowed Extensions for File UploadsGHSA-fr6r-p8hv-x3c4

MEDIUMFix: umbraco/Umbraco-CMS@d920e93

GHSA-fr6r-p8hv-x3c4 is a medium-severity (CVSS 5.5) Unrestricted File Upload vulnerability in Umbraco.Cms. A fix is available for Umbraco.Cms — see the affected versions and patch details below.

Also known asCVE-2025-48953

Published

Jun 4, 2025

Updated

Jun 5, 2025

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 5, 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 GHSA-fr6r-p8hv-x3c4.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs9th percentile — riskier than 9% of all scored CVEsHighest risk

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

.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 content management system (CMS). Starting in version 14.0.0 and prior to versions 15.4.2 and 16.0.0, it's possible to upload a file that doesn't adhere with the configured allowable file extensions via a manipulated API request. The issue is patched in versions 15.4.2 and 16.0.0. No known workarounds are available.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`Umbraco.Cms`	≥ 14.0.0&&< 15.4.2	15.4.2`dotnet add package Umbraco.Cms --version 15.4.2`

Affected Products

1 product · 1 configurations

Application

umbraco cmsumbraco

≥ 14.0.0 && < 15.4.2

range

Detection & mitigation playbook

Open-source dependency

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.
Fix
Update Umbraco.Cms to 15.4.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fr6r-p8hv-x3c4 is resolved across your whole dependency graph.
Workarounds
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

### Impact Via a manipulated API request it's possible to upload a file that doesn't adhere with the configured allowable file extensions. ### Patches Patched in 15.4.2 and 16.0.0. ### Workarounds None available.