GHSA-944X-PM95-3JPR

Vulnerability from github – Published: 2026-08-04 21:05 – Updated: 2026-08-04 21:05
VLAI
Summary
Ghost: File Upload Content-Type Spoofing
Details

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.

Severity
5.4 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Show details on source website
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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "ghost"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.19.4"
            },
            {
              "fixed": "6.21.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-53948"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-434"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-04T21:05:39Z",
    "nvd_published_at": "2026-06-24T19:17:12Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nInsufficient validation of the client-supplied `Content-Type` on Ghost\u0027s 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.\n\n### Vulnerable versions\n\nThis vulnerability is present in Ghost from v6.19.4 up to v6.21.0.\n\n### Patches\n\nv6.21.1 contains a fix for this issue.\n\n### How to update\n\nFor self-hosters using Docker, find [Docker\u0027s official Ghost image here](https://hub.docker.com/_/ghost). Updating a Docker-based Ghost instance [is documented here](https://docs.ghost.org/install/docker#updating-ghost). \n\nIf your Ghost is a Ghost-CLI install see our documentation on [updating it to the latest version here](https://docs.ghost.org/update). \n\n### For more information\n\nIf you have any questions or comments about this advisory, email us at [security@ghost.org](mailto:security@ghost.org).",
  "id": "GHSA-944x-pm95-3jpr",
  "modified": "2026-08-04T21:05:40Z",
  "published": "2026-08-04T21:05:39Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/TryGhost/Ghost/security/advisories/GHSA-944x-pm95-3jpr"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53948"
    },
    {
      "type": "WEB",
      "url": "https://github.com/TryGhost/Ghost/pull/26751"
    },
    {
      "type": "WEB",
      "url": "https://github.com/TryGhost/Ghost/commit/d659e752d6636144d75b9aa94062cdbc88a16b21"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/TryGhost/Ghost"
    },
    {
      "type": "WEB",
      "url": "https://github.com/TryGhost/Ghost/releases/tag/v6.21.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Ghost: File Upload Content-Type Spoofing"
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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