Vulnerability · Published Sep 26, 2026 · Assigned by VulnCheck

CVE-2026-100639SiYuan before v3.8.4 Cross-Site Scripting via Kramdown IAL

High 8.8

In plain English

A high-severity cross-site scripting in siyuan from siyuan-note. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities).

Severity (CVSS 3.1)8.8High

Exploit odds (30 days)0.5%top 59.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
siyuan-note	siyuan	0 – before 3.8.4

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

References

GitHub Security Advisory (GHSA-2cmm-9x9j-rvff) vendor-advisory
VulnCheck Advisory: SiYuan before v3.8.4 Cross-Site Scripting via Kramdown IAL third-party-advisory