What’s Vulnerable › Vulnerabilities

CVE-2021-4026: Improper Access Control in bookstackapp/bookstack

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-11-30 · updated 2026-06-17
• Weakness: CWE-284

Description

bookstack is vulnerable to Improper Access Control

Affected products

• bookstackapp/bookstack: before 21.11.2 — fixed in 21.11.2

How to fix

Upgrade to a fixed version: bookstackapp/bookstack 21.11.2. Check the vendor advisory for mitigations.

References

• https://github.com/bookstackapp/bookstack/commit/b4fa82e3298a15443ca40bff205b7a16a1031d92
• https://huntr.dev/bounties/c6dfa80d-43e6-4b49-95af-cc031bb66b1d
• https://github.com/bookstackapp/bookstack/commit/b4fa82e3298a15443ca40bff205b7a16a1031d92
• https://huntr.dev/bounties/c6dfa80d-43e6-4b49-95af-cc031bb66b1d

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