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.
References6
- github.com/BookStackApp/BookStack
- github.com/BookStackApp/BookStack/blob/v26.05.3/app/Uploads/Ima…
- github.com/BookStackApp/BookStack/commit/ac0348a79f3ddd004ca877…
- github.com/BookStackApp/BookStack/releases/tag/v26.05.4
- www.bookstackapp.com/blog/bookstack-release-v26-05-4/
- www.vulncheck.com/advisories/bookstack-before-26.05.4-stored-xs…
Metrics
- CVSS 3.1
-
8.7
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N - CVSS 4.0
-
9.3
CRITICAL
Score source: CNA
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:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 41 · as of 8 November 2026
- CWE
- CWE-79
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