BookStack < 26.05.4 Broken Access Control via Image Gallery API (CVE-2026-67204) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-67204

BookStack < 26.05.4 Broken Access Control via Image Gallery API

Answer in brief

CVE-2026-67204 records a Unknown severity vulnerability in BookStack < 26.05.4 Broken Access Control via Image Gallery API. The current sources do not mark it as known exploited. The current feed maps BookStackApp/BookStack (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 24, 2026Updated Aug 24, 2026Source checked Aug 24, 2026First seen by HOL Aug 24, 2026Material review Aug 24, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps BookStackApp/BookStack (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
BookStackApp/BookStackgeneric	>=0 <26.05.4	26.05.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for BookStackApp/BookStack.
Review the reported fix. Update BookStackApp/BookStack to 26.05.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 24, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.