CVE-2026-93923

Deferred Deferred - Pending Action

SiYuan Stored XSS via Unescaped Heading Style Attributes

Publication date: 2026-09-19

Last updated on: 2026-09-19

Assigner: VulnCheck

Description

SiYuan through 3.8.4 fails to escape heading style attributes when rendering outline and bookmark dock HTML, allowing stored cross-site scripting. Attackers can supply crafted notebooks or call administrative endpoints to inject malicious style values that execute in the Electron renderer with full system access.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-19

Last Modified

2026-09-19

Generated

2026-09-20

AI Q&A

2026-09-20

EPSS Evaluated

N/A

NVD

CVE-2026-93923

Affected Vendors & Products

Currently, no data is known.

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-79	The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

Attack-Flow Graph

Executive Summary

SiYuan through 3.8.4 fails to escape heading style attributes when rendering outline and bookmark dock HTML. This allows stored cross-site scripting (XSS) attacks where malicious style values can be injected into notebooks or via administrative endpoints. The injected scripts execute in the Electron renderer with full system access.

Detection Guidance

Detection involves checking for injected style attributes in SiYuan notebooks or rendered HTML. Inspect exported HTML files or network traffic for malicious style tags. No specific commands are provided in the context.

Impact Analysis

An attacker could exploit this to run arbitrary code on your system with the same privileges as the SiYuan application. This could lead to data theft, unauthorized access, or further compromise of your system. Users interacting with crafted notebooks or bookmarks are at risk.

Compliance Impact

This vulnerability could lead to unauthorized access or data breaches, violating GDPR's integrity and confidentiality requirements. For HIPAA, it may compromise protected health information integrity. Organizations using SiYuan must address this to maintain compliance with data protection regulations.

Mitigation Strategies

Upgrade SiYuan to a patched version beyond 3.8.4. Avoid importing untrusted notebooks. Review and sanitize existing notebooks for malicious style attributes. Monitor for unusual renderer behavior.

Hi! I’m here to help you understand CVE-2026-93923. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70