CVE-2026-67204

MEDIUM 5.4

BookStack < 26.05.4 Broken Access Control via Image Gallery API

CVSS Score

5.4

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-863
Vendor	bookstackapp
Product	bookstack
Published	Aug 24, 2026
Last Updated	Aug 24, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

Low

Affected Versions

BookStackApp / BookStack

0 < 26.05.4

References

NVD ↗ CVE.org ↗ EPSS Data ↗

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

Credits

ByteMe.Red VulnCheck