CVE-2026-40322 SiYuan: Mermaid `javascript:` Link Injection Leads to Stored XSS and Electron RCE
Attackers can inject JavaScript via Mermaid diagrams to achieve stored XSS and remote code execution in the Electron desktop app.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-40322?
CVE-2026-40322 is a critical cross-site scripting vulnerability in B3log Siyuan, published on 16 Apr 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
SiYuan is an open-source personal knowledge management system. In versions 3.6.3 and below, Mermaid diagrams are rendered with securityLevel set to "loose", and the resulting SVG is injected into the DOM via innerHTML. This allows attacker-controlled javascript: URLs in Mermaid code blocks to survive into the rendered output. On desktop builds using Electron, windows are created with nodeIntegration enabled and contextIsolation disabled, escalating the stored XSS to arbitrary code execution when a victim opens a note containing a malicious Mermaid block and clicks the rendered diagram node. This issue has been fixed in version 3.6.4.
Which versions are affected by CVE-2026-40322?
It affects 1 product.
Products include B3log Siyuan.
How do I fix CVE-2026-40322?
No fix has been published for CVE-2026-40322 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-40322 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40322 exists.
Other vulnerabilities in B3log Siyuan
- CVE-2026-32938 SiYuan has an Arbitrary File Read in its Desktop Publish Service
- CVE-2026-33669 SiYuan has Arbitrary Document Reading within the Publishing Service
- CVE-2026-33670 SiYuan has directory traversal within its publishing service
- CVE-2026-32767 SiYuan: Authorization Bypass Allows Arbitrary SQL Execution via Search API
- CVE-2024-53504 SQL injection in n/a
Sources
Also known as GHSA-x63q-3rcj-hhp5.