---
id: CVE-2026-75592
title: Kirby is an open-source content management system
summary: >-
  Kirby is an open-source content management system. Prior to 4.9.5 and 5.5.2,
  depending on the release line, Kirby's media handler used incomplete
  filesystem containment checks in src/Filesystem/Dir.php and
  src/Filesystem/F.php through Ki…
severity: medium
cwe:
  - CWE-22
vendor: getkirby
product: getkirby/cms
affected:
  - getkirby/cms < 4.9.5
  - 'getkirby/cms >= 5.0.0, < 5.5.2'
patched:
  - getkirby/cms 4.9.5
  - getkirby/cms 5.5.2
published: '2026-08-31'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T21:11:31.703'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-75592'
references:
  - url: >-
      https://github.com/getkirby/kirby/commit/2b6fab950bc89d505ea89576bf71c8de614cc3b2
    label: security-advisories@github.com
  - url: >-
      https://github.com/getkirby/kirby/commit/e0dca5f709adc21b36f5549df2c0619bc59da56c
    label: security-advisories@github.com
  - url: 'https://github.com/getkirby/kirby/releases/tag/4.9.5'
    label: security-advisories@github.com
  - url: 'https://github.com/getkirby/kirby/releases/tag/5.5.2'
    label: security-advisories@github.com
  - url: 'https://github.com/getkirby/kirby/security/advisories/GHSA-6j4c-mgqr-qv76'
    label: security-advisories@github.com
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-75592'
  - url: 'https://github.com/advisories/GHSA-6j4c-mgqr-qv76'
tags:
  - nvd
  - ghsa
  - composer
epss: 0.00676
epssPercentile: 0.50178
aliases:
  - GHSA-6j4c-mgqr-qv76
ecosystem: composer
ingestedAt: '2026-09-02T15:46:29.826Z'
---

## Overview

Kirby is an open-source content management system. Prior to 4.9.5 and 5.5.2, depending on the release line, Kirby's media handler used incomplete filesystem containment checks in src/Filesystem/Dir.php and src/Filesystem/F.php through Kirby\Filesystem\Dir::realpath() and Kirby\Filesystem\F::realpath(). The checks accepted a sibling directory whose path shared the intended root's string prefix, such as /var/www/site2 next to /var/www/site, because they did not require an exact match or a DIRECTORY_SEPARATOR boundary. A remote attacker could use Kirby\Cms\Media::thumb() to create and access thumbnails from image files in a PHP-readable sibling directory when that directory contained a valid .json thumbnail job file, potentially exposing staging sites, backups, or other internal sites and deleting the job file during processing. This issue is fixed in versions 4.9.5 and 5.5.2.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-75592)

Affected packages:

- `getkirby/cms < 4.9.5`
- `getkirby/cms >= 5.0.0, < 5.5.2`

Patched in:

- `getkirby/cms 4.9.5`
- `getkirby/cms 5.5.2`

Source: https://github.com/advisories/GHSA-6j4c-mgqr-qv76