CVE-2026-84695

Summary

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 Software

Weaknesses

• CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

References

• https://github.com/BookStackApp/BookStack
• https://github.com/BookStackApp/BookStack/commit/ac0348a79f3ddd004ca87703948cb9c7d19a420a
• https://github.com/BookStackApp/BookStack/blob/v26.05.3/app/Uploads/ImageService.php
• 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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