CVE-2026-72792: SiYuan Information Disclosure Vulnerability

CVE-2026-72792 Overview

CVE-2026-72792 is an information disclosure vulnerability in SiYuan, a personal knowledge management application, affecting versions prior to v3.7.4. The /api/tag/getTag endpoint returns tag labels and occurrence counts from password-protected documents without verifying the caller supplied the document's publish password. Unauthenticated readers can enumerate tag vocabulary and internal terminology sourced from protected notes by issuing a single HTTP request. The weakness is classified as an authorization bypass [CWE-863].

Critical Impact
Unauthenticated network attackers can enumerate tags and their occurrence counts from password-protected SiYuan documents, exposing internal vocabulary and project terminology.

Affected Products

SiYuan note-taking application versions prior to v3.7.4
Self-hosted SiYuan deployments exposing the HTTP API to untrusted networks
Published SiYuan documents protected by a publish password

Discovery Timeline

2026-08-12 - CVE-2026-72792 published to NVD
2026-08-12 - Last updated in NVD database

Technical Details for CVE-2026-72792

Vulnerability Analysis

SiYuan supports publishing notebooks and documents to a web-facing view protected by a publish password. Password enforcement is expected to gate any endpoint that surfaces content or metadata belonging to protected documents. The /api/tag/getTag endpoint returns aggregated tag data including labels and per-tag occurrence counts. The endpoint does not check whether the requester has authenticated against the publish password before returning tag data derived from protected documents.

An unauthenticated attacker who can reach the SiYuan HTTP interface can call this endpoint directly. The response reveals the tag vocabulary used across the workspace, which can include project codenames, client names, technology stacks, and other internal terminology. Repeated calls also expose occurrence counts, letting the attacker infer the relative importance of specific topics inside otherwise-protected notes.

Root Cause

The root cause is a missing authorization check on the tag retrieval handler. The endpoint aggregates tag metadata across all documents in scope but does not filter out entries sourced from documents that require a publish password, nor does it validate that the caller has supplied that password.

Attack Vector

Exploitation requires network access to the SiYuan API, no authentication, no user interaction, and no elevated privileges. An attacker issues a single HTTP request to /api/tag/getTag and parses the JSON response. Refer to the GitHub Security Advisory and the VulnCheck Advisory for endpoint details.

Detection Methods for CVE-2026-72792

Indicators of Compromise

Unauthenticated HTTP requests to /api/tag/getTag originating from external or unexpected internal source addresses
Repeated POST or GET requests to the tag API without an accompanying publish-password session cookie
Anomalous JSON responses from the SiYuan API returning tag inventories to clients that never authenticated

Detection Strategies

Enable HTTP access logging on the SiYuan host or upstream reverse proxy and alert on requests to /api/tag/getTag that lack an authenticated session
Compare traffic patterns against a baseline of legitimate API consumers and flag calls from IP ranges outside expected user geographies
Correlate tag API hits with subsequent enumeration of publish endpoints to identify reconnaissance activity

Monitoring Recommendations

Ingest reverse proxy and application logs into a central analytics platform for retention and query
Track the SiYuan release feed for advisories referencing GHSA-mp7r-57w4-5qm3 to confirm patch state across deployments
Alert on new external exposure of the SiYuan API surface discovered through internet-facing asset scans

How to Mitigate CVE-2026-72792

Immediate Actions Required

Upgrade SiYuan to v3.7.4 or later on every host that serves published, password-protected content
Restrict network reachability of the SiYuan API to authenticated users, VPN clients, or trusted IP ranges
Review published notebooks and rotate or remove tags that reveal sensitive project or client terminology

Patch Information

The vendor fixed the issue in SiYuan v3.7.4. Consult the GitHub Security Advisory GHSA-mp7r-57w4-5qm3 for the authoritative fix commit and release notes.

Workarounds

Place SiYuan behind a reverse proxy that requires authentication before forwarding requests to /api/tag/getTag
Block external access to the SiYuan API path at the firewall or web application firewall until the upgrade is applied
Avoid using sensitive terminology in tag names on any document intended for password-protected publishing

bash

# Example nginx block to deny unauthenticated access to the vulnerable endpoint
location = /api/tag/getTag {
    allow 10.0.0.0/8;
    deny all;
    proxy_pass http://siyuan_backend;
}