CVE-2026-53948

Ghost: File Upload Content-Type Spoofing

Vulnerable versions

This vulnerability is present in Ghost from v6.19.4 up to v6.21.0.

How to update

For self-hosters using Docker, find Docker's official Ghost image here. Updating a Docker-based Ghost instance is documented here.

If your Ghost is a Ghost-CLI install see our documentation on updating it to the latest version here.

For more information

If you have any questions or comments about this advisory, email us at [email protected].

Insufficient validation of the client-supplied Content-Type on Ghost's Admin API file upload endpoint allowed uploaded files to be served from the site with an attacker-chosen content type on S3/GCS storage backends. On installations that serve uploaded files from the same origin as the site, this could have been used to facilitate stored cross-site scripting against site visitors or staff.

The application accepts file uploads without adequately restricting the file type or content. Typical impact: remote code execution if the uploaded file can be served and executed on the server.

CVE-2026-53948 has a CVSS score of 5.4 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (6.21.1); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

v6.21.1 contains a fix for this issue.

1. What is CVE-2026-53948? CVE-2026-53948 is a medium-severity unrestricted upload of dangerous file types vulnerability in ghost (npm), affecting versions >= 6.19.4, < 6.21.1. It is fixed in 6.21.1. The application accepts file uploads without adequately restricting the file type or content.
2. How severe is CVE-2026-53948? CVE-2026-53948 has a CVSS score of 5.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of ghost are affected by CVE-2026-53948? ghost (npm) versions >= 6.19.4, < 6.21.1 is affected.
4. Is there a fix for CVE-2026-53948? Yes. CVE-2026-53948 is fixed in 6.21.1. Upgrade to this version or later.
5. Is CVE-2026-53948 exploitable, and should I be worried? Whether CVE-2026-53948 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-53948 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-53948? Upgrade ghost to 6.21.1 or later.

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