by Kastro
Paper/Archive/CVE-2026-84695

CVE-2026-84695

bookstackapp bookstack — BookStack before 26.05.4 Stored XSS via Drawing Upload

EPSS 0.5%CVSS 9.3
critical.is priorityof 100
36
CVSS 9.3 (CNA)9.3 / 10 × 3027.9Not in CISA KEV+300.0EPSS percentile 40.7.407 × 208.1No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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

ProductAffectedFixed inSource
bookstack< 26.05.426.05.4CNA

Scores by source

VulnCheck (CNA)9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
VulnCheck (CNA)8.7CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N
CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: partial

References

refgithub.com/BookStackApp/BookStackpatchgithub.com/BookStackApp/BookStack/commit/ac0348a79f3ddd004ca87703948cb9c7d19a420awriteupgithub.com/BookStackApp/BookStack/blob/v26.05.3/app/Uploads/ImageService.phprefgithub.com/BookStackApp/BookStack/releases/tag/v26.05.4advisorybookstackapp.com/blog/bookstack-release-v26-05-4writeupvulncheck.com/advisories/bookstack-before-26.05.4-stored-xss-via-drawing-upload