CVE-2023-49279
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedUmbraco is an ASP.NET content management system (CMS). Starting in version 7.0.0 and prior to versions 7.15.11, 8.18.9, 10.7.0, 11.5.0, and 12.2.0, a user with access to the backoffice can upload SVG files that include scripts. If the user can trick another user to load the media directly in a browser, the scripts can be executed. Versions 7.15.11, 8.18.9, 10.7.0, 11.5.0, and 12.2.0 contain a patch for this issue. Some workarounds are available. Implement the server side file validation or serve all media from an different host (e.g cdn) than where Umbraco is hosted.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceStored cross-site scripting (XSS) vulnerability in Umbraco CMS where authenticated backoffice users can upload SVG files containing malicious JavaScript. When another user views the SVG file directly in a browser, the embedded scripts execute, allowing session hijacking or other client-side attacks.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 7.0.0, < 7.15.11>= 8.0.0, < 8.18.9>= 10.0.0, < 10.7.0>= 11.0.0, < 11.5.0>= 12.0.0, < 12.2.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Determine installed Umbraco versionLocate the version file in the installation: for v7 check ~/bin/UmbracoCms.dll properties or Web.config version attribute; for v8+ check ~/wwwroot/bin/UmbracoCms.dll or the Version element in ~/wwwroot/appsettings.jsonAffected if The installed version falls within any of these ranges: 7.0.0 to 7.15.11, 8.0.0 to 8.18.9, 10.0.0 to 10.7.0, 11.0.0 to 11.5.0, or 12.0.0 to 12.2.0
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Verify backoffice user access to media sectionLog into the Umbraco backoffice and navigate to the Users section, then examine user groups and permissions to confirm whether any non-admin users have access to the Media section and permission to upload filesAffected if Any authenticated backoffice user (other than administrators) has permissions to upload files in the Media section
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Check if SVG media type is enabledIn the backoffice, go to Settings > Media Types and verify whether an SVG-related media type exists and is allowed, or check if the default File media type accepts .svg extension uploadsAffected if The File or a custom SVG media type is available and users can upload files with .svg extension to the media library
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Inspect existing media for SVG filesNavigate to the Media section in the backoffice and search for files with .svg extension, or check the ~/wwwroot/media folder on the server for .svg filesAffected if Any SVG files exist in the media library that were uploaded by users and are accessible via the website domain
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Confirm media serving configurationExamine appsettings.json (v8+) or Web.config (v7) to check if the MediaPath and or UseSecureMediaUrl settings are configured to serve media from a separate domain/CDN, and verify the Content Security Policy headersAffected if Media is being served from the same primary domain without a separate CDN or domain, and no CSP headers are present to block inline script execution in SVG files
You are affected if your Umbraco version is within any of the vulnerable ranges AND authenticated backoffice users can upload SVG files to the media library that are served from the same domain.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped7.15.118.18.910.7.0
Upgrade to patched versions (7.15.11, 8.18.9, 10.7.0, 11.5.0, or 12.2.0), or implement server-side validation to strip/block executable content in SVG uploads, or serve all media from a separate host/CDN domain.
7.15.11 (for v7.x), 8.18.9 (for v8.x), 10.7.0 (for v10.x), or 11.5.0 (for v11.x)
- Back up the current Umbraco installation and database before upgrading
- Review the release notes for the target fixed version to understand any changes
- In a staging environment, test upgrading to the appropriate fixed version for your current branch: 7.15.11 for v7.x, 8.18.9 for v8.x, 10.7.0 for v10.x, or 11.5.0 for v11.x
- After successful staging validation, upgrade the production environment to the fixed version
- Verify the vulnerability is remediated by confirming SVG files with scripts cannot be executed when accessed directly in a browser
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-49279 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2023-49279 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data