Answer in brief
CVE-2026-67204 records a Medium severity (CVSS 5.3) 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), 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.
CVSS is 5.3. 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.
The current feed maps BookStackApp/BookStack (generic), BookStackApp/BookStack (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| BookStackApp/BookStackgeneric | * | Not reported |
| BookStackApp/BookStackgeneric | >=0 <26.05.4 | 26.05.4 |
Published upstream
Aug 24, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 1, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 24, 2026
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.