CVE-2026-42137

Kirby CMS's pages.access/list and files.access/list permissions are not consistently checked in the Panel and REST API

Kirby's user permissions control which user role is allowed to perform specific actions to content models in the CMS. These permissions are defined for each role in the user blueprint (site/blueprints/users/...). It is also possible to customize the permissions for each target model in the model blueprints (such as in site/blueprints/pages/...) using the options feature. The permissions and options together control the authorization of user actions.

Kirby provides the pages.access, pages.list, files.access and files.list permissions (among others). The list permissions control whether affected models appear in lists throughout the Panel and REST API. The access permissions have the same effect but also disable direct access to the affected models.

In affected releases, Kirby did not consistently hide non-listable models (models for which the respective access or list permission was disabled) in the following scenarios:

• The changes dialog in the Panel listed changed models even if they were not listable.
• The REST API respected the permissions during direct model access, but did not consistently filter collections as well as related models that are included in the API responses for convenience. This includes:
  • missing permission checks for children, drafts, files, parents and siblings of pages,
  • missing permission checks for parents and siblings (next/nextWithTemplate , prev/prevWithTemplate) of files,
  • missing permission checks for children, drafts and files of the site model,
  • missing permission checks for files of users,
  • incorrect permission checks for pages.access instead of pages.list for the site and pages children and search routes and
  • incorrect permission checks for files.access instead of files.list for the account, site, pages and users files and search routes,
• The Panel images for site, pages and users were displayed in lists of the parent model even if the image files were not listable.
• The link targets for the previous and next files in the files view were not gated by the files being listable.

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

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The problem has been patched in Kirby 4.9.0 and Kirby 5.4.0. Please update to one of these or a later version to fix the vulnerability.

In all of the mentioned releases, we have added permission checks for $model->isListable() in all of the affected places. This ensures that results are filtered by the listable property, thereby enforcing the pages.access, pages.list, files.access and files.list permissions consistently.

1. What is CVE-2026-42137? CVE-2026-42137 is a high-severity missing authorization vulnerability in getkirby/cms (composer), affecting versions <= 4.8.0. It is fixed in 4.9.0, 5.4.0. The application does not perform an authorization check before performing a sensitive operation.
2. Which versions of getkirby/cms are affected by CVE-2026-42137? getkirby/cms (composer) versions <= 4.8.0 is affected.
3. Is there a fix for CVE-2026-42137? Yes. CVE-2026-42137 is fixed in 4.9.0, 5.4.0. Upgrade to this version or later.
4. Is CVE-2026-42137 exploitable, and should I be worried? Whether CVE-2026-42137 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-42137 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-42137?
   • Upgrade getkirby/cms to 4.9.0 or later
   • Upgrade getkirby/cms to 5.4.0 or later

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