CVE-2026-56385: Craft CMS Authorized Asset "preview File" Requests Vulnerability

LOW
Advisory Identifier: GHSA-44px-qjjc-xrhq
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CWE-639 CWE-862 CWE-200
Published
Advisory Summary

CVE-2026-56385 is a LOW authorized asset "preview file" requests vulnerability (CWE-639: Authorization Bypass Through User-Controlled Key) affecting Craft CMS libraries in the Packagist ecosystem. The issue involves authorized asset "preview file" requests bypass allows users without asset access to retrieve private preview metadata. Remediation is available by upgrading affected packages to version 5.9.14, 4.17.8.

CVE-2026-56385 at a Glance

CVE Identifier CVE-2026-56385
GHSA Identifier GHSA-44px-qjjc-xrhq
Severity LOW
CVSS v3.1 Base Score N/A
CWE Classification CWE-639: Authorization Bypass Through User-Controlled Key
Affected Product Craft CMS
Package Ecosystem Packagist
Published Date
Last Updated

How to Fix CVE-2026-56385

To remediate this vulnerability, upgrade all affected Craft CMS 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: 5.9.14 
Upgrade craftcms/cms to 5.9.14
craftcms/cms fixed: 4.17.8 
Upgrade craftcms/cms to 4.17.8
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 CVE-2026-56385, inspect your project dependencies for Craft CMS:

inspect dependencies for craftcms/cms

Analyze the terminal output to locate any version of Craft CMS in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.9.14), 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-639: Authorization Bypass Through User-Controlled Key, where the system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data. In Craft CMS, 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

### Summary An authenticated low-privileged user can call `assets/preview-file` for an asset they are not authorized to view and still receive preview response data (`previewHtml`) for that private asset. The returned preview HTML included a private preview image route containing the target private `assetId`, even though `canView` was `false` for the attacker account. ### Details 1. `assets/preview-file` accepts a maliciously controlled `assetId` and renders preview output. 2. The action does not enforce per-asset view authorization prior to returning preview content. 3. As a result, an authenticated user without asset-view permission can still obtain private preview output. This affects Craft installations with authenticated users of mixed privilege levels with private assets. ### Resources - d30df3112220db1ffd6726a3ed11857014c7fb27 - b1cddf72c98a

CVE-2026-56385 Affected Craft CMS Versions

2 component(s)
Fixed Versions:
5.9.144.17.8
Product / Package Ecosystem Affected Versions Fixed Version
craftcms/cms
 Packagist
≥ 5.0.0-RC1
< 5.9.14
5.9.14
craftcms/cms
 Packagist
≥ 4.0.0-RC1
< 4.17.8
4.17.8

References

NVD — CVE-2026-56385 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-56385
GitHub Advisory / Wiki ADVISORY
https://github.com/craftcms/cms/security/advisories/GHSA-44px-qjjc-xrhq
Security Fix Commit FIX COMMIT
https://github.com/craftcms/cms/commit/b1cddf72c98a66801beb04ea4b07e72182b7b7db
Security Fix Commit FIX COMMIT
https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27
Craft CMS Source Repository REPOSITORY
https://github.com/craftcms/cms
www.vulncheck.com/advisories/craft-cm... WEB
https://www.vulncheck.com/advisories/craft-cms-authorization-bypass-in-assets-preview-file-endpoint

Frequently Asked Questions

What is CVE-2026-56385?
CVE-2026-56385 is a security vulnerability in Craft CMS involving Authorized asset "preview file" requests bypass allows users without asset access to retrieve private preview metadata under CWE-639: Authorization Bypass Through User-Controlled Key.
Which Craft CMS versions are affected?
Affected versions include releases prior to 5.9.14, 4.17.8 across affected packages: craftcms/cms.
What version fixes CVE-2026-56385?
Upgrading to 5.9.14, 4.17.8 (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 5.9.14, 4.17.8. Upgrade your dependency to 5.9.14, 4.17.8 or later.
What CWE is associated with CVE-2026-56385?
CVE-2026-56385 is classified under CWE-639: Authorization Bypass Through User-Controlled Key (The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.).
How can I check Packagist dependencies for CVE-2026-56385?
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-44px-qjjc-xrhq",
  "modified" : "2026-08-06T21:56:28Z",
  "published" : "2026-03-26T17:12:21Z",
  "aliases" : [ "CVE-2026-56385" ],
  "summary" : "Craft CMS: Authorized asset \"preview file\" requests bypass allows users without asset access to retrieve private preview metadata",
  "details" : "### Summary\n\nAn authenticated low-privileged user can call `assets/preview-file` for an asset they are not authorized to view and still receive preview response data (`previewHtml`) for that private asset.\n\nThe returned preview HTML included a private preview image route containing the target private `assetId`, even though `canView` was `false` for the attacker account.\n\n### Details\n\n1. `assets/preview-file` accepts a maliciously controlled `assetId` and renders preview output.\n2. The action does not enforce per-asset view authorization prior to returning preview content.\n 3. As a result, an authenticated user without asset-view permission can still obtain private preview output.\n\nThis affects Craft installations with authenticated users of mixed privilege levels with private assets.\n\n### Resources\n\n- d30df3112220db1ffd6726a3ed11857014c7fb27\n- b1cddf72c98a",
  "severity" : [ {
    "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:U"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "craftcms/cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.0.0-RC1"
      }, {
        "fixed" : "5.9.14"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.9.13"
    }
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "craftcms/cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0-RC1"
      }, {
        "fixed" : "4.17.8"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.17.7"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/security/advisories/GHSA-44px-qjjc-xrhq"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-56385"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/commit/b1cddf72c98a66801beb04ea4b07e72182b7b7db"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/craftcms/cms/commit/d30df3112220db1ffd6726a3ed11857014c7fb27"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/craftcms/cms"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/craft-cms-authorization-bypass-in-assets-preview-file-endpoint"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-200", "CWE-639", "CWE-862" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-26T17:12:21Z",
    "nvd_published_at" : null
  }
}