# 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.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H`)
- **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 available:** No
- **Published:** 16 Apr 2026
- **Updated:** 17 Apr 2026
- **Also known as:** GHSA-x63q-3rcj-hhp5

## 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.

Weakness: CWE-94 (Improper Control of Generation of Code), CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-40322?

It affects 1 product.


Products: 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.

## 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](https://insights.sbomify.com/CVE-2026-32938/): SiYuan has an Arbitrary File Read in its Desktop Publish Service (critical 9.9)
- [CVE-2026-33669](https://insights.sbomify.com/CVE-2026-33669/): SiYuan has Arbitrary Document Reading within the Publishing Service (critical 9.8)
- [CVE-2026-33670](https://insights.sbomify.com/CVE-2026-33670/): SiYuan has directory traversal within its publishing service (critical 9.8)
- [CVE-2026-32767](https://insights.sbomify.com/CVE-2026-32767/): SiYuan: Authorization Bypass Allows Arbitrary SQL Execution via Search API (critical 9.8)
- [CVE-2024-53504](https://insights.sbomify.com/CVE-2024-53504/): SQL injection in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40322 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40322 exists.

Affected product: B3log Siyuan. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40322/ (Markdown: https://insights.sbomify.com/CVE-2026-40322/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40322
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40322
- OSV: https://osv.dev/vulnerability/CVE-2026-40322

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40322/
Summaries are generated and may contain mistakes; the official description above is the record.