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

> Authenticated users can modify or delete other users' avatars via the Image Gallery API due to missing authorization checks.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 24 Aug 2026
- **Updated:** 1 Oct 2026
- **Also known as:** GHSA-v32j-vgqh-f22g

## What is CVE-2026-67204?

CVE-2026-67204 is a medium-severity missing authorization vulnerability in BookStackApp BookStack, published on 24 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### 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.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-67204?


## How do I fix CVE-2026-67204?

No fix has been published for CVE-2026-67204 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-67204 being exploited?

There is no known exploitation of CVE-2026-67204 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-67204 and fix it if it is affected.

What it is: CVE-2026-67204 is a medium-severity missing authorization vulnerability in BookStackApp BookStack, published on 24 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-67204 in the wild and no public exploit code.

Affected product: BookStackApp BookStack. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-67204/ (Markdown: https://insights.sbomify.com/CVE-2026-67204/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-67204
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-67204
- OSV: https://osv.dev/vulnerability/CVE-2026-67204

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-67204/
Summaries are generated and may contain mistakes; the official description above is the record.