# CVE-2026-103276: Ghost file extension filtering bypass in theme serving

Source: https://junglewise.ai/threats/cve-2026-103276-ghost-versions-before-6-20-0-contain-a-file-extension-filtering  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-01. Updated: 2026-10-05  
License: CC BY 4.0 with a link back

CVE-2026-103276 · Severity: medium · CVSS 5.3 · Published 2026-10-01

Ghost is a publishing platform used to host blogs and websites. Versions before 6.20.0 contain a vulnerability that allows unauthenticated attackers to read sensitive theme files by bypassing file extension validation through URL encoding. An attacker could access theme templates and metadata that should not be publicly visible.

Technologies: [TryGhost Ghost](https://junglewise.ai/threats/technologies/tryghost-ghost). Vendors: [TryGhost](https://junglewise.ai/threats/vendors/tryghost).

## Quick answers

**Is CVE-2026-103276 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-103276 being exploited in the wild.

**How severe is CVE-2026-103276?** Medium severity, with a CVSS score of 5.3, published 1 October 2026.

**Which products and versions are affected?** TryGhost Ghost before 6.20.0.

**Is there a fix for CVE-2026-103276?** Yes: fixed in 6.20.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-103276 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-103276?** Check whether you run TryGhost Ghost at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 6.20.0

## Technical details

The vulnerability is an improper handling of alternate encoding (CWE-173) in Ghost's theme file serving mechanism. Unauthenticated attackers can exploit URL encoding to bypass extension-based access controls on theme files, gaining read access to theme templates and metadata. The issue requires only network access with no authentication or user interaction.

## Affected products

- TryGhost Ghost before 6.20.0

## Timeline

- 2026-08-13: disclosed
- 2026-10-01: advisory

## References

- [https://github.com/TryGhost/Ghost/security/advisories/GHSA-6v8p-3jx9-8chr](https://github.com/TryGhost/Ghost/security/advisories/GHSA-6v8p-3jx9-8chr)
- [https://www.vulncheck.com/advisories/ghost-before-6.20.0-file-read-via-url-encoding-bypass](https://www.vulncheck.com/advisories/ghost-before-6.20.0-file-read-via-url-encoding-bypass)

## Related threats

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- [Ghost content type validation bypass in local file storage](https://junglewise.ai/threats/cve-2026-105679-ghost-is-a-node-js-content-management-system-from-6-22-1-until-6)
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