CVE-2025-48953Network attack vector

Disallowed file upload via untrimmed extension

Published Jun 3, 2025 · Updated Jun 3, 2025

Unrestricted file upload in Umbraco CMS 14.0.0 through 15.4.1 allows remote authenticated users to bypass extension controls. The IsFileAllowedForUpload method compares the request-supplied extension without trimming whitespace, so a suffixed value evades allowlist or denylist matching. Backoffice access and a manipulated API request are required; the uploaded file can violate the configured policy, but code execution is not established.

CVSS severity5.5
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unrestricted file upload in Umbraco CMS 14.0.0 through 15.4.1 allows remote authenticated users to bypass extension controls. The IsFileAllowedForUpload method compares the request-supplied extension without trimming whitespace, so a suffixed value evades allowlist or denylist matching. Backoffice access and a manipulated API request are required; the uploaded file can violate the configured policy, but code execution is not established.

The record

CVE
CVE-2025-48953
Published
Jun 3, 2025
Updated
Jun 3, 2025
Vendor
Umbraco
Product
Umbraco CMS
Classifications
CWE-434
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 3, 2025CVE publishedPublication date reported by the CVE source.
  2. Jun 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 14.0.0, < 15.4.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Umbraco · Umbraco CMSversion=>= 14.0.0, < 15.4.2

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
5.5GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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