CVE-2026-53943: Ghost: Cache-poisoning XSS in Ghost frontend via x-ghost-preview header
Impact
When Ghost is behind a shared caching layer that results in cached content being shared between different visitors (e.g., Fastly, Cloudflare, nginx proxycache, and others), an unauthenticated user could send an x-ghost-preview header that altered the rendered frontend response. In affected cache configurations, that response could be stored and served to subsequent visitors requesting the same page, allowing cache poisoning of request-specific preview output.
When running Ghost's frontend and admin panel on the same domain this could be used to take over staff user accounts. When running these on different domains staff accounts have no exposure.
Vulnerable versions
This vulnerability is present in Ghost from v4.0 up to v6.36.0.
Patches
v6.37.0 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.
If you suspect a credential compromise, use the “Reset all authentication” dialogue under Settings / Danger Zone. This is available starting with Ghost v6.41.0.
Workarounds
At the caching layer, bypass the cache for x-ghost-preview requests.
References
Ghost thanks CryptoCat for disclosing this vulnerability responsibly.
For more information
If you have any questions or comments about this advisory, email us at security@ghost.org.
Other sources
Ghost is a Node.js content management system. From until 6.37.0, when Ghost is behind a shared caching layer that results in cached content being shared between different visitors, an unauthenticated user could send an x-ghost-preview header that altered the rendered frontend response. In affected cache configurations, that response could be stored and served to subsequent visitors requesting the same page, allowing cache poisoning of request-specific preview output. When running Ghost's frontend and admin panel on the same domain this could be used to take over staff user accounts. When running these on different domains staff accounts have no exposure. This vulnerability is fixed in 6.37.0.
— NVD
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/ghostto a version that resolves this vulnerability.Fixed in 6.37.0 - Upgrade
Upgrade
Ghostto a version that resolves this vulnerability.Fixed in 6.37.0 - Compensating control
At the caching layer, bypass the cache for `x-ghost-preview` requests so cached content cannot be poisoned by preview-rendered responses.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-53943?
CVE-2026-53943 has a critical severity rating of 9.6.
How do I fix CVE-2026-53943?
To mitigate CVE-2026-53943, upgrade Ghost to version 6.37.0 or later.
What type of vulnerability is CVE-2026-53943?
CVE-2026-53943 is a cache-poisoning cross-site scripting (XSS) vulnerability.
Who is affected by CVE-2026-53943?
Any Ghost installations prior to version 6.37.0 that use a shared caching layer are affected by CVE-2026-53943.
How can an attacker exploit CVE-2026-53943?
An attacker can exploit CVE-2026-53943 by sending a crafted x-ghost-preview header to alter the frontend response for different users.