CVE-2026-84695

HIGH 8.7

BookStack before 26.05.4 Stored XSS via Drawing Upload

CVSS Score

8.7

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-79
Vendor	bookstackapp
Product	bookstack
Published	Sep 2, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

Affected Versions

bookstackapp / bookstack

0 < 26.05.4

References

NVD ↗ CVE.org ↗ EPSS Data ↗

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

Credits

Emanuele Cervelli