TI-2026-80089 Aliases CVE-2026-116020 GHSA-m83h-jfmj-p8jm

Incorrect authorization in BookStack attachment controller exposes draft pages

LOW 23CWE-863Published 2026-10-24 · Updated 2026-11-05

Key facts

Attack vector: Network
Privileges required: Low
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Security bypass
Confidentiality · integrity · availability: Low · Low · None
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-863.

Summary

BookStack before 26.09.2 contains an incorrect authorization flaw in AttachmentController that lets authenticated users access attachments on other users' draft pages by ID. An attacker with attachment permissions can enumerate sequential attachment IDs to download, rename, relink, or replace files on another user's unpublished draft pages (CWE-863). Exploitation requires low privileges over the network and no user interaction, and the impact is limited to confidentiality and integrity of the affected attachments.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Description from the CNA

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permissions can enumerate sequential attachment IDs to download, rename, relink, or replace files on another user's unpublished draft pages.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00181 7th percentileScored 2026-11-07

Fix Fixed BookStack (BookStackApp): 26.09.2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
bookstackapp	BookStack	before 26.09.2	26.09.2	Patch available	CNA

BookStack Vendorbookstackapp Affected before 26.09.2 Fixed in 26.09.2 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:bookstackapp:bookstack::::::::	—	—	bookstackapp

cpe:2.3:a:bookstackapp:bookstack:*:*:*:*:*:*:*:* Versions — — ·bookstackapp

Remediation

Update BookStack to version 26.09.2 or later, which fixes this issue.

Written with Claude Haiku 5.5 from the sources below · 2026-10-28

Fix · CNA BookStack (BookStackApp) Fixed in 26.09.2

Timeline

2026-10-24 Threatist record created from CVE-2026-116020
2026-10-24 Alias added: GHSA-m83h-jfmj-p8jm
2026-11-05 CISA SSVC decision points changed

References

Patch 1

https://codeberg.org/bookstack/bookstack/commit/fcadecccda706b4ecaf9ac3f8e27defe0ebe78ae

Advisory 1

https://www.bookstackapp.com/blog/bookstack-release-v26-09-2/

Other 2

TI-2026-04803 BookStackApp BookStack Chapter Export ExportFormatter.php chapterToMarkdown access control CVSS 4.0MEDIUM 6.9
TI-2021-02995 Improper Access Control in bookstackapp/bookstack CVSS 3.1CRITICAL 9.8
TI-2023-04263 Server-Side Request Forgery (SSRF) in bookstackapp/bookstack CVSS 3.1LOW 2.4
TI-2026-60332 BookStack < 26.05.5 Authentication Bypass via Social Login Provider Confusion CVSS 4.0CRITICAL 9.1
TI-2026-56847 BookStack before 26.05.4 Remote Code Execution via Book Cover CVSS 4.0HIGH 8.7
TI-2020-04312 Remote Code Execution Through Image Uploads in BookStack CVSS 3.1HIGH 8.8

See all 26 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences