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medium·Product Based Web Vulnerabilities·Updated Apr 6, 2026

CVE-2026-31809 Scanner

CVE-2026-31809 Scanner - Cross-Site Scripting (XSS) vulnerability in SiYuan

Est. Time~10 seconds
Scan TypeSingle Scan
Targetsurl
CostFree
2.8k
Times Used
continuous scan runs
4.1k
Continuously Checked
assets under CS
0
Vulnerabilities Found
confirmed findings
References
CVECVE-2026-31809
6.4
CVSSmedium
Exploitable remotely over the internet · no authentication required.

SiYuan is a personal knowledge management system. Prior to 3.5.10, SiYuan's SVG sanitizer (SanitizeSVG) checks href attributes for the javascript: prefix using strings.HasPrefix(). However, inserting ASCII tab (	), newline (
), or carriage return (
) characters inside the javascript: string bypasses this prefix check. Browsers strip these characters per the WHATWG URL specification before parsing the URL scheme, so the JavaScript still executes. This allows an attacker to inject executable JavaScript into the unauthenticated /api/icon/getDynamicIcon endpoint, creating a reflected XSS. This is a second bypass of the fix for CVE-2026-29183 (fixed in v3.5.9). This vulnerability is fixed in 3.5.10.

Attack Vector
Network
Privileges Req.
None
User Interaction
P
Affected
siyuanby siyuan-note
< 3.5.10
Updated Aug 22, 2026View on NVD →
Detail

SiYuan is a software application used widely by individuals and organizations for managing notes and documentation. It is designed to help users organize their thoughts and knowledge efficiently. The platform is utilized in educational and professional settings to foster collaboration and information sharing. SiYuan facilitates the creation and structuring of digital content, making it valuable for various research and development fields. Its user interface provides a seamless experience for content management and retrieval. The software is crucial in environments where documentation and note-taking are integral to daily operations.

The detected vulnerability is a Cross-Site Scripting (XSS) issue found in SiYuan versions up to 3.5.9. XSS vulnerabilities allow attackers to inject malicious scripts into web pages viewed by other users, potentially leading to session hijacking or other client-side attacks. This vulnerability arises due to improper sanitization of JavaScript href attributes in the SVG sanitizer. Unauthenticated attackers can exploit this weakness to execute arbitrary JavaScript in the browsers of users accessing the compromised SiYuan instance. It poses a significant risk of unauthorized data access and session manipulation.

The technical details surrounding this vulnerability involve the improper handling of href attributes in SVG elements, allowing ASCII control characters to bypass security checks. Attackers craft malicious input to exploit the /api/icon/getDynamicIcon endpoint in SiYuan, triggering unsafe script execution. The vulnerable parameter pertains to how dynamic icons are retrieved utilizing unsafe JavaScript execution paths. Furthermore, the exploit involves sending a crafted request to the affected endpoint, which, when accessed by a victim's browser, executes the attacker's injected script.

The possible effects of this vulnerability being exploited include unauthorized access to user sessions and sensitive information. Attackers could hijack user sessions, leading to potential identity theft or data manipulation. Additionally, it could serve as a gateway for conducting further client-side attacks and spreading malware. Exploitation of this issue undermines trust in the affected SiYuan environments, posing privacy and security risks to users. It is crucial to address this issue promptly to maintain the security integrity of systems using the affected version.

REFERENCES

Solution Advice
  • Upgrade to SiYuan version 3.5.10 or later to patch the vulnerability.
  • Enhance security practices by implementing strict input validation and output encoding for all user-supplied data.
  • Conduct a comprehensive review of code to ensure all user data is sanitized before processing.
  • Regularly update and patch software components to mitigate potential security vulnerabilities.
  • Consider employing Content Security Policy (CSP) to add an additional layer of security against XSS attacks.

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CVE-2026-31809 Scanner - Cross-Site Scripting (XSS) vulnerability in SiYuan | S4E