Vulnerability Description
SiYuan v3.8.3 fails to HTML-escape the data-subtype attribute when generating gutter-button markup (app/src/protyle/gutter/button.ts, assigned via innerHTML in app/src/protyle/gutter/index.ts) from content pasted as plain-text Markdown containing a Kramdown inline attribute list (IAL). Because the shared Lute renderer parses Kramdown IAL from text/plain input, an attacker-supplied Markdown snippet using entity-encoded quotes in data-subtype breaks out of the attribute value when the gutter markup is re-parsed by the browser, injecting additional attributes such as autofocus and onfocus. If a victim pastes the crafted Markdown and the affected gutter control receives focus, the injected handler executes; in the Electron desktop application, where the main BrowserWindow enables Node integration and disables context isolation, this results in JavaScript execution with renderer Node.js privileges (remote code execution). Fixed in v3.8.4.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-2cmm-9x9j-rvff
- https://www.vulncheck.com/advisories/siyuan-before-3.8.4-cross-site-scripting-vi
- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-2cmm-9x9j-rvff
FAQ
What is CVE-2026-100639?
CVE-2026-100639 is a vulnerability with a CVSS score of 8.8 (HIGH). SiYuan v3.8.3 fails to HTML-escape the data-subtype attribute when generating gutter-button markup (app/src/protyle/gutter/button.ts, assigned via innerHTML in app/src/protyle/gutter/index.ts) from co...
How severe is CVE-2026-100639?
CVE-2026-100639 has been rated HIGH with a CVSS base score of 8.8/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-100639?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.