CVE-2026-84695

High

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.

SeverityHigh

CVSS8.7

Exploit probability—

Product

Bookstack

PublishedSep 2, 2026

First seenSep 2, 2026

Weakness typeCWE-79Cross-site scripting (XSS)

How to fix

Update

bookstackapp bookstack26.05.4 or later

Patches

github.com/BookStackApp/BookStack/commit/ac0348a79f3ddd004ca87703948cb9c7d19a420a

Vendor advisories

Affected products

Product	Affected versions	Fixed in
bookstackapp bookstack	v < 26.05.4	26.05.4

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