What’s Vulnerable › Vulnerabilities

CVE-2026-67204: BookStack < 26.05.4 Broken Access Control via Image Gallery API

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-24 · updated 2026-10-12
• Weakness: CWE-863

Description

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.

Affected products

• bookstackapp/bookstack: before 26.05.4 — fixed in 26.05.4

How to fix

Upgrade to a fixed version: bookstackapp/bookstack 26.05.4. Check the vendor advisory for mitigations.

References

• https://codeberg.org/bookstack/bookstack/releases/tag/v26.05.4
• https://github.com/BookStackApp/BookStack/releases/tag/v26.05.4
• https://www.bookstackapp.com/blog/bookstack-release-v26-05-4/
• https://www.vulncheck.com/advisories/bookstack-broken-access-control-via-image-gallery-api

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