Vulnerability · Published Sep 2, 2026 · Assigned by VulnCheck

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

High 8.7

In plain English

A high-severity cross-site scripting in bookstack from bookstackapp. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities).

Severity (CVSS 3.1)8.7High

Exploit odds (30 days)0.5%top 59.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 (as reported)

Vendor	Product	Versions
bookstackapp	bookstack	0 – before 26.05.4

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

References

https://github.com/BookStackApp/BookStack product
Patch Commit patch
https://github.com/BookStackApp/BookStack/blob/v26.05.3/app/Uploads/ImageService.php technical-description
BookStack v26.05.4 Release Notes release-notes
https://www.bookstackapp.com/blog/bookstack-release-v26-05-4/ vendor-advisory
VulnCheck Advisory: BookStack before 26.05.4 Stored XSS via Drawing Upload third-party-advisory