External risk intelligence

SiYuan Content Endpoints Leak Publish Forbidden Documents

CVE advisorySeverity: CRITICAL (CVSS 9.2)

CVE-2026-68586

SiYuan is a note-taking application that features a publish mode designed to expose content to the internet. Because the vulnerable API endpoints are reachable within this public-facing publishing feature, it is common for these deployments to be accessible from the public internet.

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A vulnerability exists in SiYuan before version 3.7.3 that could allow unauthorized access to unpublished document content through specific API endpoints. This issue arises because access controls are not consistently applied, potentially exposing rendered content and reference information to unauthenticated users, especially in environments where publish-mode authentication is disabled.

Unpublished content can be accessed via APIs.
Note-taking app's publish feature is exposed.
Confirm if publishing is enabled and users are authenticated.

Attack Path

How an attacker could exploit the issue

An attacker can access sensitive information by exploiting a flaw in how SiYuan handles content visibility settings. Specifically, certain API endpoints designed to retrieve document references do not correctly enforce restrictions on content that should not be published. This allows an attacker, even one without any login, to query these endpoints directly and uncover details about private documents, including whether they contain specific content or link to other documents.

Requires access to the SiYuan application.
Triggers by querying specific content API endpoints.
Risks exposure of private document content.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow unauthorized access to rendered document content and block reference information within SiYuan, even when those documents are marked as forbidden from publishing. This exposure is possible when the application's publish-access filters are not correctly applied to specific content endpoints, potentially enabling a user without appropriate permissions to query sensitive document details.

Unrestricted access to rendered document content.
Direct calls to content endpoints can expose data.
Information disclosure regarding document references.

Operational Fix

Recommended remediation, mitigation, and detection steps

SiYuan application owners and platform teams should lead remediation efforts for this vulnerability, as it affects the note-taking application's content endpoints. The first practical step is to identify all SiYuan instances, especially those using the publish mode, confirm their internet reachability and business criticality, and then engage the appropriate teams to plan remediation based on risk.

Application owners must resolve the issue.
Verify affected SiYuan instances and their reachability.
Plan and coordinate remediation with affected teams.

Supplementary metadata

CVSS vector

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Frequently asked questions

What is SiYuan?

SiYuan is a local-first, open-source note-taking application that supports structured data and block-level referencing. It features a publish mode that allows users to share specific notes or entire knowledge bases on the web. This software is designed for personal knowledge management, where users organize complex information, often involving internal links and private document structures.

What does CWE-862 mean for CVE-2026-68586?

CWE-862 is the classification for Missing Authorization. In the context of CVE-2026-68586, this means the software fails to verify if a user has permission to view a specific document before serving its data. While SiYuan correctly checks permissions for document lists, the affected API endpoints skip these checks, inadvertently allowing unauthorized access to the rendered content of sensitive files.

How is this vulnerability triggered?

An attacker triggers this by sending direct requests to the /api/ref/getBacklinkDoc or /api/ref/getBackmentionDoc endpoints. By providing the unique ID of a document that is marked as publish-forbidden, the attacker can force the system to return that document's content. Simply visiting the public site normally does not trigger this; the exploit requires knowledge of internal document IDs and the ability to interact with these specific backend API paths.

Is my SiYuan instance at risk?

Your risk is higher if your SiYuan instance is internet-facing, as Halo Surface Signal notes this application is frequently deployed with its publish mode exposed to the public. If your setup allows anonymous access to the web-published version of your notes—or if you have disabled publish-mode authentication—external users could potentially query these internal endpoints to view documents you intended to keep private.

What should I do to secure my SiYuan installation?

The most effective way to address this is to upgrade to SiYuan version 3.7.3 or later, which contains the necessary security fixes. In the meantime, identify all your SiYuan instances to see which ones have the publish feature enabled. Review your access configurations, ensure that any necessary authentication is strictly enforced, and prioritize restricting network access to sensitive management interfaces until you can complete the upgrade.

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.