OCTOBER 9, 2026
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Case File

CVE-2026-100639

HIGH · CVSS 8.8 EPSS 0.47% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-09-26 · Last synced 2026-10-09

CyberRota Analysis

AI-Generated

The vulnerability affects SiYuan v3.8.3, where improper HTML escaping of the data-subtype attribute in gutter-button markup allows attackers to inject malicious attributes through crafted Markdown input. This can lead to remote code execution in environments like the Electron desktop application, where Node integration is enabled. Organizations using this version of SiYuan should prioritize upgrading to v3.8.4 to mitigate the risk of exploitation.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Detected Signals
remote code execution code execution
GitHub PoC Links

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2026-100639
Severity
HIGH
CVSS
8.8
EPSS
0.47%
Java

Original NVD 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.