CVE-2026-53948

mediumCVSS 5.4covered by 1 sourcefirst seen 2026-08-04

Impact 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. Vulnerable versions This vulnerability is present in Ghost from v6.19.4 up to v6.21.0. Patches v6.21.1 contains a fix for this issue. 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 security@ghost.org.

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Exploitation outlook

Low exploitation risk0.13% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all EPSS-scored CVEs.

Advisory coverage (1)

mediumGHSA-944x-pm95-3jpr: Ghost: File Upload Content-Type Spoofingghsa · 2026-08-04

External references

NVD record for CVE-2026-53948

CVE.org record

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