SiYuan EUVD-2026-57452

Exploitation requires network access to a SiYuan instance and the presence of at least one document protected by SiYuan's publish password feature. The attacker requires no credentials, session tokens, or authentication of any kind - the /api/tag/getTag endpoint is reachable without supplying the document's publish password. Exploitation is bounded to tag labels and occurrence counts; full document body content is not disclosed by this endpoint. SiYuan instances that are not exposed to untrusted networks (e.g., localhost-only deployments with no reverse proxy or port forwarding) and instances whose password-protected documents contain no sensitive tag vocabulary have no meaningful exposure.

The CVSS 4.0 score of 6.9 (Medium) reflects a genuine but bounded risk: the vulnerability is trivially exploitable (AV:N, AC:L, AT:N, PR:N, UI:N) but the impact is limited to low confidentiality disclosure of tag metadata rather than document content (VC:L, SC:L, all integrity and availability metrics at N). There is no CISA KEV listing and no public exploit code identified, and no EPSS score was provided in the input - exploitation probability cannot be quantified from available data. The practical risk is highly context-dependent: for deployments where SiYuan stores sensitive personal, legal, medical, or corporate intelligence, tag vocabulary alone may reveal enough to cause real harm; for low-sensitivity personal note-taking instances not exposed to untrusted networks, impact is negligible. The absence of any authentication requirement means that network-exposed instances require no attacker sophistication whatsoever. No conflicting signals exist between the CVSS vector and the description - both consistently indicate unauthenticated network exploitation with limited informational impact.

An attacker with network access to an exposed SiYuan instance sends an unauthenticated HTTP GET request to the /api/tag/getTag endpoint. The API returns all tag labels and their document occurrence counts without verifying the caller has the publish password for the protected documents. By iterating through available tag data, the attacker reconstructs a vocabulary map of topics, projects, or entities present in the protected knowledge base without ever accessing document content.