---
id: CVE-2026-67204
title: >-
  BookStack before 26.05.4 contains a broken access control vulnerability that
  allows authenticated API users with image-update or image-delete permissions
  to manipulate other users' avatars by exploiting missing content-type
  restrictions …
summary: >-
  BookStack before 26.05.4 contains a broken access control vulnerability that
  allows authenticated API users with image-update or image-delete permissions
  to manipulate other users' avatars by exploiting missing content-type
  restrictions …
severity: medium
cvss: 5.4
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L'
cwe:
  - CWE-863
published: '2026-08-24'
updated: '2026-09-24'
sourceUpdated: '2026-09-24T20:43:32.537'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-67204'
references:
  - url: 'https://codeberg.org/bookstack/bookstack/releases/tag/v26.05.4'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/BookStackApp/BookStack/releases/tag/v26.05.4'
    label: disclosure@vulncheck.com
  - url: 'https://www.bookstackapp.com/blog/bookstack-release-v26-05-4/'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/bookstack-broken-access-control-via-image-gallery-api
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.00413
epssPercentile: 0.32797
ingestedAt: '2026-09-24T20:51:40.223Z'
---

## Overview

BookStack before 26.05.4 contains a broken access control vulnerability that allows authenticated API users with image-update or image-delete permissions to manipulate other users' avatars by exploiting missing content-type restrictions in the Image Gallery API endpoints. Attackers can supply a user avatar's ID to the API controller, which loads any image type without the web controller's gallery and drawio restrictions, and when the avatar's uploaded_to field matches a page ID accessible to the attacker, the authorization check passes allowing the attacker to rename, replace, or delete the target user's avatar without requiring user-management permission.

## Remediation

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