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MEDIUM severity

bookstack is vulnerable to Improper Access ControlGHSA-ghhm-xrwp-75m9

MEDIUMFix: bookstackapp/bookstack@cb0d674

GHSA-ghhm-xrwp-75m9 is a medium-severity (CVSS 4.3) CWE-284 vulnerability in ssddanbrown/bookstack. 2 public exploit references exist, so weaponization risk is real. A fix is available for ssddanbrown/bookstack — see the affected versions and patch details below.

Also known asCVE-2021-4194
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
2 known
Exploitation data as of Oct 13, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs52th percentile — riskier than 52% of all scored CVEsHighest risk
0.00%0.40%0.80%1.21%0.2%0.7%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-ghhm-xrwp-75m9 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐘ssddanbrown/bookstack

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

bookstack is vulnerable to Improper Access Control

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistssddanbrown/bookstackall versions21.12.1composer require ssddanbrown/bookstack:^21.12.1

Affected Products

1 product · 1 configurations
Application
bookstackbookstackapp
< 21.12.1
range
Exploits & PoCs
2

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

bookstack is vulnerable to Improper Access Control

huntr.devNVDJan 2022

bookstack is vulnerable to Improper Access Control

github.comNVDJan 2022

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ssddanbrown/bookstack, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update ssddanbrown/bookstack to 21.12.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-ghhm-xrwp-75m9 is resolved across your whole dependency graph.

  3. Workarounds

    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

bookstack is vulnerable to Improper Access Control
O3 Security · Impact-Aware SCA

Is GHSA-ghhm-xrwp-75m9 in your dependencies?

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bookstack is vulnerable to Improper Access Control