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

Status: published. Published: 2026-10-24. Updated: 2026-11-05.

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permissions can enumerate sequential attachment IDs to download, rename, relink, or replace files on another user's unpublished draft pages.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://codeberg.org/bookstack/bookstack/commit/fcadecccda706b4ecaf9ac3f8e27defe0ebe78ae

## Affected products and versions

- BookStackApp / BookStack: ≥ 0; < 26.09.2 (affected, custom). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 5.3 (medium); 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; source: CNA: VulnCheck

- CVSS 3.1: 5.4 (medium); CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: 0.18% as of 2026-11-05; percentile 7.74%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-863

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://codeberg.org/bookstack/bookstack/commit/fcadecccda706b4ecaf9ac3f8e27defe0ebe78ae (CNA: VulnCheck; patch)

- https://www.bookstackapp.com/blog/bookstack-release-v26-09-2/ (CNA: VulnCheck; vendor-advisory, release-notes)

- https://codeberg.org/bookstack/bookstack/releases/tag/v26.09.2 (CNA: VulnCheck; release-notes)

- https://codeberg.org/bookstack/bookstack/src/tag/v26.09.1/app/Uploads/Controllers/AttachmentController.php (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/bookstack-before-26.09.2-incorrect-authorization-via-attachmentcontroller-on-draft-pages (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-116020; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-116020; retrieved 2026-11-05; source updated Not reported

Revision: 847359df38e5667f976f9523313eabb796e3ceaaf2f3574f03935da2732f6e02

Canonical: https://y2.dev/cve/CVE-2026-116020

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