Vulnerability · Published Aug 24, 2026 · Assigned by VulnCheck

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

Medium 5.4

In plain English

A medium-severity incorrect authorization in BookStack from BookStackApp. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 36% of all known vulnerabilities).

Severity (CVSS 3.1)5.4Medium

Exploit odds (30 days)0.4%top 64.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 (as reported)

Vendor	Product	Versions
BookStackApp	BookStack	0 – before 26.05.4

Weakness: CWE-863 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

References

Maintainer Blog vendor-advisory
Codeberg Release Notes release-notes
BookStack v26.05.4 Release Notes release-notes
https://www.vulncheck.com/advisories/bookstack-broken-access-control-via-image-gallery-api third-party-advisory