Auth bypass in Bookstackapp Bookstack
CVE-2026-116020
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permissions can enumerate sequential attachment IDs to download, rename, relink, or replace files on another user's unpublished draft pages.
Vulnerability class: Broken Access Control
Published .
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- codeberg.org/bookstack/bookstack/commit/fcadecccda706b4ecaf9ac3f8e27defe0ebe78ae (patch)
- www.bookstackapp.com/blog/bookstack-release-v26-09-2/ (release-notes, vendor-advisory)
- codeberg.org/bookstack/bookstack/releases/tag/v26.09.2 (release-notes)
- codeberg.org/bookstack/bookstack/src/tag/v26.09.1/app/Uploads/Controllers/Attac… (technical-description)
- www.vulncheck.com/advisories/bookstack-before-26.09.2-incorrect-authorization-v… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-116020?
- CVE-2026-116020 is a medium-severity vulnerability in Bookstackapp Bookstack, classified under Incorrect Authorization. CVSS score: 5.4/10. Published 2026-10-24.
- How severe is CVE-2026-116020?
- Medium severity. CVSS v3 base score is 5.4 out of 10.