VulnerabilityPublished 24 Jun 2026

CVE-2026-53948: TryGhost Ghost · Unrestricted File Upload

Affects TryGhost GhostSource CVE Database V5

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Not known to be exploited · CVSS 5.4 Medium : upgrade to 6.21.1 when convenient.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 3.1 base score

5.4Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 13% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 6.21.1

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: Required
Scope: Changed
Confidentiality: Low
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 24 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade TryGhost Ghost to 6.21.1.

Affected software

Product	Affected	Fixed in
TryGhostGhost	Affected >=6.19.4 <6.21.1	Fixed in 6.21.1

AI-suggested

A fix is available in Ghost version 6.21.1. For cloud-hosted instances, the vendor manages remediation server-side. Users should upgrade to version 6.21.1 or later to address this vulnerability. Until patched, administrators should be cautious about file uploads and serving uploaded files from the same origin.

Description

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.

Impact

An attacker can upload files with attacker-controlled content types that are served from the site, potentially enabling stored cross-site scripting attacks against site visitors or administrative staff. This can lead to partial compromise of confidentiality and integrity via script execution in the context of the vulnerable site. Availability is not impacted. The vulnerability requires at least low privileges and user interaction.

Summary

Ghost CMS versions >=6.19.4 and <6.21.1 have a CWE-434 vulnerability where the Admin API file upload endpoint does not properly validate the Content-Type header supplied by clients. This allows attackers to upload files that are served with arbitrary content types on S3/GCS storage backends. When files are served from the same origin as the site, this can facilitate stored cross-site scripting (XSS) attacks. The vulnerability has a CVSS 3.1 base score of 5.4 (medium severity) and is fixed in version 6.21.1. The product is a cloud service, so the vendor manages remediation for hosted instances.

CWE-434Unrestricted Upload of File with Dangerous Type (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #12OWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.
Architecture and Design
Generate a new, unique filename for an uploaded file instead of using the user-supplied filename, so that no external input is used at all.
Architecture and Design · Enforcement by Conversion
When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
Architecture and Design
Consider storing the uploaded files outside of the web document root entirely. Then, use other mechanisms to deliver the files dynamically.
OWASP Cheat Sheets
Server Side Request Forgery Prevention (opens in a new tab)
Web Service Security (opens in a new tab)
Third Party Javascript Management (opens in a new tab)
File Upload (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V12.5.2 (opens in a new tab)
V13.1.5 (opens in a new tab)
V12.2.1 (opens in a new tab)
Attack patterns
Accessing Functionality Not Properly Constrained by ACLs (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/TryGhost/Ghost/security/advisories/GHSA-944x-pm95-3jpr (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 1 Jul 2026, 22:44 UTC

WeaknessesCWE-434

Technical details

References

Community reviews

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