---
id: "CVE-2026-116020"
kind: "vulnerability"
aliases: ["CVE-2026-116020"]
title: "BookStack: authenticated users can read and change other users' draft attachments"
severity: "medium"
cvss: 5.4
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["bookstack", "package", "php", "self-hosted"]
not_affected_if: ["default-config", "single-user"]
published_at: "2026-10-24T12:16:58+00:00"
first_seen_at: "2026-10-24T12:47:58+00:00"
updated_at: "2026-10-25T04:14:10+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-116020", "first_seen_at": "2026-10-24T12:47:58+00:00"}]
---

# BookStack: authenticated users can read and change other users' draft attachments

BookStack versions before 26.09.2 let any logged-in user reach attachments on other users' unpublished draft pages by guessing sequential attachment IDs. An attacker can download, rename, relink or replace those files.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed BookStack version in the app's footer or `composer.lock` / release tag; versions below `26.09.2` are affected.
- Confirm an account has attachment permissions before assuming exposure: the description says attackers need them.

## Fix

- Upgrade BookStack to `26.09.2` or later.
- Until upgraded, review which users hold attachment permissions and limit them to trusted accounts.

## Timeline

- 2026-10-24T12:47:58+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-116020

## From the sources

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permissions can enumerate sequential attachment IDs to download, rename, relink, or replace files on another user's unpublished draft pages.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_