# CVE-2026-116020: BookStack before 26.09.2 Incorrect Authorization via AttachmentController on Draft Pages


- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 24 Oct 2026
- **Updated:** 24 Oct 2026
- **Also known as:** GHSA-m83h-jfmj-p8jm

## What is CVE-2026-116020?

CVE-2026-116020 is a medium-severity vulnerability in BookStackApp BookStack, published on 24 Oct 2026. 

### Official description

BookStack before 26.09.2 contains an incorrect authorization vulnerability in AttachmentController that allows authenticated users to access other users' draft page attachments by ID. Attackers with attachment permissions can enumerate sequential attachment IDs to download, rename, relink, or replace files on another user's unpublished draft pages.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-116020?


## How do I fix CVE-2026-116020?

No fix has been published for CVE-2026-116020 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-116020 being exploited?

There is no known exploitation of CVE-2026-116020 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-116020 and fix it if it is affected.

What it is: CVE-2026-116020 is a medium-severity vulnerability in BookStackApp BookStack, published on 24 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-116020 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-2026-116020/ (Markdown: https://insights.sbomify.com/CVE-2026-116020/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-116020
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-116020
- OSV: https://osv.dev/vulnerability/CVE-2026-116020

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-116020/
Summaries are generated and may contain mistakes; the official description above is the record.