GHSA-xj2c-g5xp-4p47: Duplicate Advisory Craft CMS: Authenticated "assets/preview-thumb" Discloses Vulnerability

MODERATE
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CVSS 4.3
CWE-862
Published
Advisory Summary

GHSA-xj2c-g5xp-4p47 is a MODERATE (CVSS 4.3) craft cms: authenticated "assets/preview-thumb" discloses vulnerability (CWE-862: Missing Authorization) affecting Duplicate Advisory libraries in the Packagist ecosystem. The issue involves craft cms: authenticated "assets/preview-thumb" discloses signed fallback transform preview link to cp users without asset-view permission. Remediation is available in the latest vendor maintenance releases.

GHSA-xj2c-g5xp-4p47 at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-xj2c-g5xp-4p47
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-862: Missing Authorization
Affected Product Duplicate Advisory
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 4.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix GHSA-xj2c-g5xp-4p47

To remediate this vulnerability, upgrade all affected Duplicate Advisory dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

craftcms/cms fixed: Latest secure release 
Upgrade craftcms/cms to Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for craftcms/cms

How to Check if You Are Affected

To determine whether your application is affected by GHSA-xj2c-g5xp-4p47, inspect your project dependencies for Duplicate Advisory:

inspect dependencies for craftcms/cms

Analyze the terminal output to locate any version of Duplicate Advisory in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-862: Missing Authorization, where the product does not perform an authorization check when an actor attempts to access a resource or perform an action. In Duplicate Advisory, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-x76w-8c62-48mg. This link is maintained to preserve external references. ## Original Description Craft CMS contains a missing authorization vulnerability in the assets/preview-thumb endpoint. A Control Panel user without permission to view a target private asset can call the endpoint with an attacker-controlled assetId and receive preview HTML containing a signed fallback transform preview link for that private asset, because no asset-view permission check is performed before preview generation. This affects versions >= 4.0.0-RC1, <= 4.17.7 and >= 5.0.0-RC1, <= 5.9.13, and is fixed in 4.17.8 and 5.9.14.

GHSA-xj2c-g5xp-4p47 Affected Duplicate Advisory Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
craftcms/cms
 Packagist
≥ 4.0.0-RC1
≤ 4.17.7

References

GitHub Advisory / Wiki ADVISORY
https://github.com/craftcms/cms/security/advisories/GHSA-x76w-8c62-48mg
NVD — GHSA-xj2c-g5xp-4p47 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-56384
Security Fix Commit FIX COMMIT
https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27
www.vulncheck.com/advisories/craft-cm... WEB
https://www.vulncheck.com/advisories/craft-cms-missing-authorization-in-assets-preview-thumb-endpoint

Frequently Asked Questions

What is GHSA-xj2c-g5xp-4p47?
GHSA-xj2c-g5xp-4p47 is a security vulnerability in Duplicate Advisory involving Craft CMS: Authenticated "assets/preview-thumb" discloses signed fallback transform preview link to CP users without asset-view permission under CWE-862: Missing Authorization.
Which Duplicate Advisory versions are affected?
Affected versions include releases prior to current release patches across affected packages: craftcms/cms.
What version fixes GHSA-xj2c-g5xp-4p47?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is craftcms/cms affected?
Yes, craftcms/cms is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of GHSA-xj2c-g5xp-4p47?
GHSA-xj2c-g5xp-4p47 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.
What CWE is associated with GHSA-xj2c-g5xp-4p47?
GHSA-xj2c-g5xp-4p47 is classified under CWE-862: Missing Authorization (The product does not perform an authorization check when an actor attempts to access a resource or perform an action.).
How can I check Packagist dependencies for GHSA-xj2c-g5xp-4p47?
Run the dependency tree command: 'inspect dependencies for craftcms/cms'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xj2c-g5xp-4p47",
  "modified" : "2026-08-06T21:06:06Z",
  "published" : "2026-06-21T15:31:24Z",
  "withdrawn" : "2026-08-06T21:06:06Z",
  "aliases" : [ ],
  "summary" : "Duplicate Advisory: Craft CMS: Authenticated \"assets/preview-thumb\" discloses signed fallback transform preview link to CP users without asset-view permission",
  "details" : "## Duplicate Advisory\n\nThis advisory has been withdrawn because it is a duplicate of GHSA-x76w-8c62-48mg. This link is maintained to preserve external references.\n\n## Original Description\nCraft CMS contains a missing authorization vulnerability in the assets/preview-thumb endpoint. A Control Panel user without permission to view a target private asset can call the endpoint with an attacker-controlled assetId and receive preview HTML containing a signed fallback transform preview link for that private asset, because no asset-view permission check is performed before preview generation. This affects versions >= 4.0.0-RC1, <= 4.17.7 and >= 5.0.0-RC1, <= 5.9.13, and is fixed in 4.17.8 and 5.9.14.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "craftcms/cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0-RC1"
      }, {
        "last_affected" : "4.17.7"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/security/advisories/GHSA-x76w-8c62-48mg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-56384"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/craft-cms-missing-authorization-in-assets-preview-thumb-endpoint"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-862" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-06T21:06:06Z",
    "nvd_published_at" : "2026-06-21T14:16:26Z"
  }
}