Bookstack Cross-site Scripting vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.7 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

EPSS

• CVE-2020-26211: 1.10% estimated exploitation activity in the next 30 days; percentile 65.61 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

In BookStack before version 0.30.4, a user with permissions to edit a page could insert JavaScript code through the use of javascript: URIs within a link or form which would run, within the context of the current page, when clicked or submitted. Additionally, a user with permissions to edit a page could insert a particular meta tag which could be used to silently redirect users to a alternative location upon visit of a page. Dangerous content may remain in the database but will be removed before being displayed on a page. If you think this could have been exploited the linked advisory provides a SQL query to test. As a workaround without upgrading, page edit permissions could be limited to only those that are trusted until you can upgrade although this will not address existing exploitation of this vulnerability. The issue is fixed in BookStack version 0.30.4.

Published by the source

24 May 2022, 17:32 UTC

Last modified by the source

20 Jul 2023, 14:49 UTC

Source last checked

26 Oct 2026, 14:06 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-ch37-ch8w-cfrq

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# Patch Next advisory brief: CVE-2020-26211

Advisory: Bookstack Cross-site Scripting vulnerability
IDs: CVE-2020-26211, GHSA-ch37-ch8w-cfrq
Record: https://patchnext.com/advisories/cve-2020-26211 (revision 1, source checked 26 Oct 2026, 14:06 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ssddanbrown/bookstack 0.30.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist ssddanbrown/bookstack: affected < 0.30.4; fixed in 0.30.4

## Suggested inspection (read-only)
- Packagist ssddanbrown/bookstack: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ssddanbrown/bookstack.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-ch37-ch8w-cfrq (GitHub-reviewed advisory GHSA-ch37-ch8w-cfrq lists affected ranges: Packagist ssddanbrown/bookstack >=0 <0.30.4)

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