CVE-2026-65606 in SiYuan
Summary
by MITRE • 07/23/2026
SiYuan before v3.7.2 contains a cross-site scripting vulnerability in the siyuan:// protocol handler. When a siyuan://plugins/<name> link references a name that is not an installed plugin, the application opens a custom tab and inserts the link's icon parameter into the tab header via innerHTML without escaping it (app/src/layout/Tab.ts), allowing injection of an <img onerror=...> element. Because the SiYuan Desktop renderer runs with nodeIntegration:true, the injected JavaScript can access Node's require and call require('child_process').execSync(...), escalating the cross-site scripting into arbitrary operating-system command execution.
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Analysis
by VulDB Data Team • 07/23/2026
This vulnerability exists within the SiYuan desktop application version prior to 3.7.2 and represents a critical cross-site scripting flaw that can be exploited to achieve arbitrary code execution on the underlying operating system. The vulnerability stems from improper input sanitization within the siyuan:// protocol handler implementation, specifically in how the application processes plugin links that reference non-existent plugins. When such a link is processed, the application creates a custom tab and directly inserts the icon parameter into the tab header using innerHTML without any HTML escaping or sanitization measures. This primitive injection point allows attackers to inject malicious html elements including script tags that can execute arbitrary JavaScript code within the application's context.
The security implications of this vulnerability extend far beyond typical cross-site scripting limitations due to the application's desktop environment configuration. SiYuan Desktop operates with nodeIntegration:true which grants the renderer process access to Node.js APIs and system-level capabilities. This configuration means that any JavaScript code executed within the renderer can leverage Node.js's require function to load modules including child_process, which provides access to operating system command execution capabilities. The exploitation chain begins with a simple cross-site scripting payload that injects a script tag containing malicious code, which then leverages the elevated privileges of nodeIntegration to execute arbitrary commands on the host system.
The technical flaw resides in the Tab.ts file within the application's layout component where the icon parameter is directly inserted into the DOM using innerHTML instead of proper sanitization techniques. This pattern violates fundamental security principles for handling user-provided input and demonstrates a classic lack of input validation and output encoding practices. The vulnerability affects the siyuan://plugins/ protocol handler specifically when processing links that reference plugins not installed on the system, making it particularly insidious as it can be triggered through various attack vectors including malicious web pages or phishing campaigns that direct users to crafted siyuan:// URLs.
This vulnerability aligns with CWE-79 (Cross-site Scripting) and CWE-116 (Improper Encoding or Escaping of Output), while also demonstrating characteristics consistent with ATT&CK technique T1059.007 (Command and Scripting Interpreter: PowerShell) through the use of child_process.execSync for command execution. The attack surface is expanded by the desktop application's architecture that permits renderer processes to access system-level APIs, effectively bypassing typical browser sandbox restrictions. Organizations using SiYuan Desktop should be particularly concerned as this vulnerability allows attackers to execute arbitrary commands with the privileges of the user running the application, potentially leading to complete system compromise.
The operational impact of this vulnerability extends beyond simple data theft or defacement to encompass full system control and persistence capabilities. Attackers can leverage this vulnerability to install malicious software, exfiltrate sensitive data, establish backdoors, or perform other malicious activities that would normally require physical access or elevated privileges. The vulnerability's exploitability is relatively straightforward since it requires only the user to click on a crafted siyuan:// URL, making it particularly dangerous in social engineering campaigns or when users encounter malicious content in web browsers or email clients that may trigger the protocol handler.
The recommended mitigations include immediate patching of SiYuan Desktop to version 3.7.2 or later where the vulnerability has been addressed through proper input sanitization and output encoding of user-provided parameters. Additionally, organizations should implement network-level protections such as URL filtering and protocol handler restrictions to prevent users from inadvertently triggering malicious siyuan:// links. The application's developers should also consider implementing Content Security Policy headers and stricter input validation mechanisms for all user-provided content that gets rendered in the UI. Users should be educated about the risks of clicking on untrusted links and the potential consequences of executing desktop applications with elevated privileges through protocol handlers.
The vulnerability demonstrates a critical gap in security practices within desktop application development, particularly regarding the handling of protocol handlers and the use of nodeIntegration in Electron-based applications. This type of issue highlights the importance of following secure coding practices including input validation, output encoding, and principle of least privilege when designing applications that bridge web and native system capabilities. The attack vector emphasizes the need for comprehensive security testing of desktop applications including protocol handler implementations and proper sandboxing mechanisms to prevent escalation from web-based attacks to system-level compromises.