---
title: "CVE-2026-100641: SiYuan - Stored XSS"
description: "SiYuan before v3.8.4 contains a stored XSS caused by lack of HTML-escaping in flashcard block content in card-manager list markup, letting authenticated administrators execute arbitrary code, exploit requires admin role and attacker-supplied content."
url: https://panop.io/threat-heartbeat/CVE-2026-100641/
---

# CVE-2026-100641 SiYuan - Stored XSS

SiYuan before v3.8.4 contains a stored XSS caused by lack of HTML-escaping in flashcard block content in card-manager list markup, letting authenticated administrators execute arbitrary code, exploit requires admin role and attacker-supplied content.

CVSS base score 8.0 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Required

EPSS

0.53% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-100641)

## Details

Type

Stored XSS

Impact

Remote Code Execution

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

Published

26 September 2026

Updated

15 October 2026

Weakness

[CWE-79](https://cwe.mitre.org/data/definitions/79.html)

## Vendor fix

Update to version v3.8.4 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-100641](https://nvd.nist.gov/vuln/detail/CVE-2026-100641)
- [https://github.com/siyuan-note/siyuan/commit/1ecb1c07de497ff03b585536fe5579291754d96b](https://github.com/siyuan-note/siyuan/commit/1ecb1c07de497ff03b585536fe5579291754d96b)
- [https://github.com/siyuan-note/siyuan/commit/41b14025b4ac4a8379d1200580344ca18ad152b7](https://github.com/siyuan-note/siyuan/commit/41b14025b4ac4a8379d1200580344ca18ad152b7)
- [https://github.com/siyuan-note/siyuan/commit/48c354e7de130aaada9d7120125bbc768344fd3b](https://github.com/siyuan-note/siyuan/commit/48c354e7de130aaada9d7120125bbc768344fd3b)
- [https://github.com/siyuan-note/siyuan/commit/8641553a1f07374001902d3ce773285db1292b2d](https://github.com/siyuan-note/siyuan/commit/8641553a1f07374001902d3ce773285db1292b2d)
- [https://github.com/siyuan-note/siyuan/security/advisories/GHSA-2mmf-4xwm-55rm](https://github.com/siyuan-note/siyuan/security/advisories/GHSA-2mmf-4xwm-55rm)
- [https://www.vulncheck.com/advisories/siyuan-before-3.8.4-stored-xss-via-unescaped-flashcard-content](https://www.vulncheck.com/advisories/siyuan-before-3.8.4-stored-xss-via-unescaped-flashcard-content)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

Panop answers these inside your environment, for this CVE and every other finding.

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