# CVE-2026-100641: SiYuan before v3.8.4 Stored XSS via Unescaped Flashcard Content

> Stored XSS in SiYuan allows attackers to execute arbitrary code on the host via malicious flashcard content processed by the privileged Electron renderer.

- **Severity:** High 8.6 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **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:** 26 Sep 2026
- **Updated:** 5 Oct 2026
- **Also known as:** GHSA-2mmf-4xwm-55rm, GHSA-wvmc-29rv-83j2

## What is CVE-2026-100641?

CVE-2026-100641 is a high-severity cross-site scripting vulnerability in siyuan-note siyuan, published on 26 Sep 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 before v3.8.4 does not HTML-escape stored flashcard block content before interpolating it into the card-manager list markup. Block content returned by /api/riff/getRiffCards is inserted into a card item template in app/src/card/viewCards.ts and assigned to listElement.innerHTML, so content such as <img src=invalid onerror=...> becomes an executable event-handler attribute. Because the SiYuan desktop (Electron) main window is created with nodeIntegration enabled and contextIsolation disabled, an administrator who opens the card manager on a workspace containing attacker-supplied flashcard content (for example introduced through contribution or import) executes the attacker's script in a privileged renderer, which can lead to arbitrary code execution on the host. The affected endpoint remains behind authentication and administrator-role checks; this is an untrusted-content-to-privileged-renderer issue, not an authorization bypass.

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

## Which versions are affected by CVE-2026-100641?


## How do I fix CVE-2026-100641?

No fix has been published for CVE-2026-100641 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-100641 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100641 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-100641 and fix it if it is affected.

What it is: CVE-2026-100641 is a high-severity cross-site scripting vulnerability in siyuan-note siyuan, published on 26 Sep 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-2026-100641 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-2026-100641/ (Markdown: https://insights.sbomify.com/CVE-2026-100641/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-100641
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100641
- OSV: https://osv.dev/vulnerability/CVE-2026-100641

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-100641/
Summaries are generated and may contain mistakes; the official description above is the record.