External risk intelligence

SiYuan Stored XSS to OS Command Execution Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.0)

CVE-2026-34448

SiYuan is a local, individual knowledge management tool. The vulnerability requires manual user interaction to view specific malicious content within the desktop client. Because it lacks public-facing network services or shared infrastructure, the attack surface for remote, automated exploitation is extremely limited.

Cross-site Scripting

B3log Siyuan

before 3.6.2

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

SiYuan, a personal knowledge management system, has a critical vulnerability that could allow an attacker to execute arbitrary commands on a user's computer. This occurs if a user with limited access clicks on a malicious link, which then leads to the execution of code when they view specific content within the application. The issue is present in versions prior to 3.6.2.

Malicious links can execute commands on user computers.
Leadership should remember this issue due to potential data compromise.
Confirm relevance and exposure within your organization.

Attack Path

How an attacker could exploit the issue

An attacker with the ability to modify an Attribute View's mAsse field can exploit this vulnerability. By inserting a malicious URL into this field, they can trigger stored cross-site scripting (XSS) when a victim views the Gallery or Kanban with a specific cover image setting enabled. In the desktop client, this XSS can lead to arbitrary operating system command execution.

Attacker places malicious URL in mAsse field.
Victim opens Gallery or Kanban view with cover image.
Arbitrary OS command execution is possible.

Live Threat

Current exploitation, exposure, and threat context

A malicious URL placed in an Attribute View field can lead to stored XSS when a victim views a Gallery or Kanban view with specific settings enabled in the SiYuan desktop client. This could allow arbitrary operating system command execution on the victim's machine when the injected JavaScript is processed.

System data and user files.
Victim opens malicious content in the app.
Arbitrary OS command execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

The SiYuan knowledge management system's Electron client is vulnerable to stored cross-site scripting (XSS) leading to OS command execution. This impacts users who view a malicious URL placed in an Attribute View's "mAsse" field, specifically when the Gallery or Kanban view with "Cover From -> Asset Field" enabled is opened. The primary action for system owners is to identify all instances of SiYuan, assess their reachability and criticality, and then coordinate remediation with relevant teams, potentially including application owners and security teams, to mitigate the risk.

Identify SiYuan deployments and ownership.
Verify exposure and business criticality.
Plan remediation based on risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is SiYuan?

SiYuan is a personal knowledge management system designed for individual note-taking and information organization. It functions as a desktop application built on the Electron framework, allowing users to store and structure their own data locally. Because it is intended for individual use, it is typically managed as a standalone tool on personal or workstation computers rather than as a shared server application.

How does CVE-2026-34448 work?

This vulnerability involves Stored Cross-Site Scripting (CWE-79) and Code Injection (CWE-94). The application fails to properly validate URLs entered into specific data fields. When a user views this data in certain layouts, the software treats the malicious input as active code. Because of the way the desktop client is configured, this allows the injected script to escape the application sandbox and execute unauthorized commands directly on the user's operating system.

Do I need to be concerned about network triggers?

No. This issue is not triggered by automated network scanning or remote probes. An attacker must successfully place a malicious URL into a specific data field within the application. The vulnerability remains dormant until the victim actively opens a affected view—specifically the Gallery or Kanban view—with the 'Cover From' setting enabled. Simply having the software installed or connected to a network does not initiate the execution process.

Is my SiYuan instance at risk?

Halo Surface Signal indicates that the risk of automated remote exploitation is very unlikely, as SiYuan is a local, individual tool lacking public-facing services. You are only at risk if you are using a version prior to 3.6.2 and perform the specific user actions required to render the malicious content. The danger is highest in environments where users might import or sync untrusted, externally-created data files containing malicious attribute fields.

How do I address this CVE?

The primary and most effective step is to update your SiYuan installation to version 3.6.2 or later, as this release contains the necessary patches to sanitize input and prevent the execution of arbitrary commands. If you cannot update immediately, avoid enabling the 'Cover From -> Asset Field' setting in Gallery or Kanban views when dealing with notes from untrusted sources, and ensure you are aware of all individuals who have permission to modify data attributes within your notes.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.