# CVE-2026-66395: SiYuan Desktop before v3.7.2 Reflected XSS to RCE via siyuan Protocol

> Attackers can execute arbitrary code with Node.js privileges by crafting malicious deep links that trigger reflected XSS in the plugin readme handler.

- **Severity:** Critical 9.4 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 27 Jul 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-6gx2-8gcr-x83f, GHSA-x52j-m89g-wh64

## What is CVE-2026-66395?

CVE-2026-66395 is a critical cross-site scripting vulnerability in siyuan-note siyuan, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

SiYuan desktop before v3.7.2 contains a reflected cross-site scripting vulnerability in the bazaar plugin readme handler that allows attackers to execute arbitrary code by crafting a malicious siyuan:// deep link. Attackers can inject HTML payloads via the plugin name parameter that execute with full Node.js access through insertAdjacentHTML rendering in an insecurely configured Electron renderer.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-66395?


## How do I fix CVE-2026-66395?

No fix has been published for CVE-2026-66395 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-66395 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-66395 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66395 and fix it if it is affected.

What it is: CVE-2026-66395 is a critical cross-site scripting vulnerability in siyuan-note siyuan, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, 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-2026-66395 exists.

Affected product: siyuan-note 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-2026-66395/ (Markdown: https://insights.sbomify.com/CVE-2026-66395/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66395
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66395
- OSV: https://osv.dev/vulnerability/CVE-2026-66395

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-66395/
Summaries are generated and may contain mistakes; the official description above is the record.