What is CVE-2026-84695?

CVE-2026-84695 is a high-severity vulnerability in Bookstackapp Bookstack, classified under Cross-site Scripting. CVSS score: 8.7/10. Published 2026-09-02.

How severe is CVE-2026-84695?

High severity. CVSS v3 base score is 8.7 out of 10.

XSS in Bookstackapp Bookstack

CVE-2026-84695

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.

Vulnerability class: XSS (Cross-Site Scripting)

CVSS v3 metric

CVSS v3 base score 8.7 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N.

Affected products

Bookstackapp Bookstack

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

disclosure@vulncheck.com (product)
disclosure@vulncheck.com (technical-description)
disclosure@vulncheck.com (patch)
disclosure@vulncheck.com (release-notes)
disclosure@vulncheck.com (vendor-advisory)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-84695?: CVE-2026-84695 is a high-severity vulnerability in Bookstackapp Bookstack, classified under Cross-site Scripting. CVSS score: 8.7/10. Published 2026-09-02.
How severe is CVE-2026-84695?: High severity. CVSS v3 base score is 8.7 out of 10.