CVE-2026-100643 in SiYuan
Summary
by MITRE • 09/26/2026
SiYuan versions before v3.8.4 fail to properly escape four stored Attribute View values in textarea elements, allowing authenticated attackers to inject JavaScript by modifying field descriptions, template sources, select option descriptions, or footer calculation templates. Attackers can execute stored JavaScript when other users open affected database menus, and in the Electron desktop app with nodeIntegration enabled, this leads to command execution with SiYuan process privileges.
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Analysis
by VulDB Data Team • 09/26/2026
The vulnerability identified in SiYuan versions prior to v3.8.4 represents a critical security flaw rooted in improper input validation and output encoding within the application's database management interface. Specifically, the software fails to properly escape four distinct types of stored Attribute View values when rendering them inside HTML textarea elements. These vulnerable fields include field descriptions, template sources, select option descriptions, and footer calculation templates. The core technical failure lies in the absence of adequate sanitization or encoding mechanisms for user-supplied data that is subsequently rendered back into the browser context without proper escaping. This oversight allows an authenticated attacker to inject malicious JavaScript payloads directly into these database fields. Because SiYuan operates as a web-based application with desktop variants, this flaw exploits the trust relationship between the client and the server-side stored content, turning static data storage into a vector for active code execution.
From an operational perspective, this vulnerability facilitates Stored Cross-Site Scripting attacks that can have severe consequences depending on the deployment environment of SiYuan. In standard web browser contexts, successful exploitation allows attackers to execute arbitrary JavaScript in the context of other users who open affected database menus. This enables session hijacking, credential theft through keylogging or cookie stealing, and defacement of the user interface. The impact escalates significantly when utilizing the Electron desktop application with nodeIntegration enabled. In this configuration, the injected JavaScript gains access to Node.js APIs, effectively granting the attacker command execution capabilities with the privileges of the SiYuan process on the host operating system. This transforms a typical web vulnerability into a full remote code execution vector, allowing for complete compromise of the victim's machine, including file system access and network reconnaissance.
This flaw is classified under CWE-79 Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting, specifically in its stored variant where malicious scripts are permanently stored on target servers. The attack vector aligns with MITRE ATT&CK technique T1059 Command and Scripting Interpreter, particularly when leveraging Node.js capabilities within the Electron environment to execute system commands. Additionally, it relates to CWE-83 Improper Neutralization of Special Elements used in an SQL Command if one considers the broader context of data handling failures, though the primary impact is script injection rather than database manipulation. The vulnerability highlights a common pitfall in modern web applications where rich text editors and dynamic form elements are not sufficiently sanitized against complex payload structures that bypass basic filtering rules.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. Users should immediately upgrade to SiYuan version v3.8.4 or later, which addresses the input validation issues in the affected textarea rendering logic. For administrators managing deployments of the Electron desktop application, it is critical to review security configurations regarding nodeIntegration. Disabling nodeIntegration where not strictly necessary reduces the blast radius of any potential client-side vulnerabilities by preventing JavaScript from accessing native system APIs. Furthermore, implementing a robust Content Security Policy can help mitigate the impact of successful script injection attempts by restricting the sources from which scripts can be loaded and executed. Regular security audits focusing on input validation across all user-editable fields are essential to prevent similar flaws in future development cycles.