Arbitrary file upload in Tryghost Ghost

CVE-2026-53948

Ghost is a Node.js content management system. From 6.19.4 until 6.21.1, 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. This vulnerability is fixed in 6.21.1.

Vulnerability class: Unrestricted File Upload

Published · last modified .

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.002 (12.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 12th percentile — 12.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-53948: held from 0.002 to 0.002.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-53948?
CVE-2026-53948 is a medium-severity vulnerability in Tryghost Ghost, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 5.4/10. Published 2026-06-24.
How severe is CVE-2026-53948?
Medium severity. CVSS v3 base score is 5.4 out of 10.