What’s Vulnerable › Vulnerabilities

CVE-2026-84695: BookStack before 26.05.4 Stored XSS via Drawing Upload

• Severity: high (CVSS 8.7 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-02 · updated 2026-09-08
• Weakness: CWE-79

Description

BookStack before 26.05.4 contains a stored cross-site scripting vulnerability in the drawing upload endpoint that accepts unvalidated base64 content and stores it without content inspection. Attackers with editor permissions can upload SVG files containing scripts that execute in administrator browsers when accessed through the image gallery API without content-type validation or CSP headers.

Affected products

• bookstackapp/bookstack: before 26.05.4 — fixed in 26.05.4

How to fix

Upgrade to a fixed version: bookstackapp/bookstack 26.05.4. Check the vendor advisory for mitigations.

References

• https://github.com/BookStackApp/BookStack
• https://github.com/BookStackApp/BookStack/blob/v26.05.3/app/Uploads/ImageService.php
• https://github.com/BookStackApp/BookStack/commit/ac0348a79f3ddd004ca87703948cb9c7d19a420a
• https://github.com/BookStackApp/BookStack/releases/tag/v26.05.4
• https://www.bookstackapp.com/blog/bookstack-release-v26-05-4/
• https://www.vulncheck.com/advisories/bookstack-before-26.05.4-stored-xss-via-drawing-upload

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