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Why is Umbraco CMS v13.x flagged for a vulnerability, and what steps should I take?

Joana Knobbe avatar
Written by Joana Knobbe
Updated over 3 weeks ago

Why is Umbraco CMS v13.x flagged for a vulnerability, and what steps should I take?

Overview

Visual Studio or other vulnerability scanners may flag Umbraco CMS v13.x (e.g., versions 13.12.1 and 13.13.0) for a potential security issue related to server-side file validation (CVE warning). This article explains the cause of the warning, whether action is required, and how to address the underlying risk.

Understanding the CVE Warning

The vulnerability warning refers to an issue where Umbraco CMS does not include built-in server-side validation for file uploads. Uploaded files, if not validated on the server, could contain malicious content, such as scripts leading to stored cross-site scripting (XSS) attacks.

This is not a newly introduced vulnerability. The flagged CVE duplicates an earlier report on the same topic and stems from Umbraco’s flexibility to allow developers to implement server-side validation according to their unique project requirements.

It is not a regression or new defect in the CMS platform and does not directly imply an immediate security risk if proper validation practices are already in place.

For reference, this issue is highlighted in CVE-2025-67288 and CVE-2023-49279, but these identifiers may change as duplicate entries are merged or updated.

Do You Need to Take Action?

Whether you are vulnerable depends entirely on your implementation:

  1. If You Have Server-Side Validation: - If your project already includes proper server-side file validation, you are not exposed to this vulnerability. You can ignore the CVE warning flagged by security tools safely.

  2. If You Do Not Have Server-Side Validation: - Introduce server-side file validation for uploads as outlined in Umbraco’s best practices to mitigate any potential risks. This step ensures uploaded files are thoroughly checked for malicious content before processing or storage.

Note: The flagged warning may persist in vulnerability scanners until the duplicate entries in vulnerability databases are consolidated and removed.

For reference, our guidance on implementing server-side file validation can be found here: https://docs.umbraco.com/umbraco-cms/reference/security/serverside-file-validation

Why Isn’t There a Patch or Hotfix?

Umbraco CMS does not include default server-side file validation by design to provide developers with flexibility for implementation. This is not considered a vulnerability or defect within the platform's architecture, and as such, no patches or hotfixes are planned for the flagged CVE warnings in version 13.x. The responsibility for validation rests with the developers using Umbraco. To secure your application, adhere to Umbraco’s guidance for implementing server-side validation. This proactive measure will safeguard against malicious file uploads regardless of the flagged CVE warning.

Key Takeaways

  • The CVE warnings for Umbraco CMS do not indicate a new or emergent threat.

  • Developers must implement server-side file validation to address potential risks.

  • The warnings may persist until duplicate CVEs are merged in vulnerability databases.

By understanding the root causes and taking the recommended actions, you can ensure your applications remain secure while ignoring unnecessary false positives in your tools.

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