CVE-2026-84695: bookstackapp bookstack

BookStack before 26.05.4 Stored XSS via Drawing Upload

CVSS 9.3 CriticalCriticalEPSS 0.0047 · 40th percentile

Critical, because:

CVSS score 9.3: 9.0 or more.

Published by the CVE Program (CNA: VulnCheck) at 2 Sept 2026, 00:37 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. This CVE names a vendor and product rather than a package, so the lockfile check doesn’t match it.

Affected products, as the CNA wrote them
Vendor	Product	Versions
bookstackapp	bookstack https://github.com/BookStackApp/BookStack pkg:github/BookStackApp/BookStack	affected before 26.05.4 custom unaffected 26.05.4 custom Other versions: unaffected

Identifiers

CVE-2026-84695

CNA

VulnCheck

Weakness (CWE)

CWE-79

Not analysed yet

We haven’t published our own analysis of this CVE. If a person reviews it, this page will say what’s affected and what has to be true for it to matter.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
9.3	Critical	4.0	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N	CNA (VulnCheck)Used for this record
8.7	High	3.1	CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N	CNA (VulnCheck)

CISA KEV Not listed.
EPSS 0.0047, the 40th percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the CVE Program, published 2 Sept 2026. New records show when each source confirmed them.

Sources

References from the CNA

github.com/BookStackApp/BookStack product
github.com/BookStackApp/BookStack/commit/ac0348a79f3ddd004ca87703948cb9c7d19a420a patch
github.com/BookStackApp/BookStack/blob/v26.05.3/app/Uploads/ImageService.php technical-description
github.com/BookStackApp/BookStack/releases/tag/v26.05.4 release-notes
www.bookstackapp.com/blog/bookstack-release-v26-05-4/ vendor-advisory
www.vulncheck.com/advisories/bookstack-before-26.05.4-stored-xss-via-drawing-upload third-party-advisory

Facts on this page come from the CVE List as the CNA published them, with CVSS from the sources named above, CISA KEV and FIRST EPSS. Vendors, products and versions are shown as the CNA wrote them. We don’t reproduce the CVE’s description.