Vulnerability record · CVE-2026-84695 · published 2 September 2026

CVE-2026-84695: Cross-site scripting vulnerability

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.

9.3 CVSS 4.0 Critical EPSS 0.47% · top 61.8% CWE-79 · Cross-site scripting Deferred

9.3CVSS 4.0 base score

0.47%EPSS exploitation probability, 30 days

NoNot in CISA KEV

0Affected product versions listed by NVD

6References

8 Sep 2026Last modified by NVD

Description

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

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

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Source: NIST National Vulnerability Database (record CVE-2026-84695), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.