SiYuan EUVD-2026-57813

Exploitation requires that the SiYuan instance is running a version prior to v3.7.4 and its HTTP API server is network-reachable from the attacker (internet-exposed or accessible on the local network). No authentication is required per the CVSS 4.0 vector (PR:N, UI:N). No special workspace configuration, specific feature enablement, or publish-mode activation is required to trigger the vulnerability - the getBookmarkLabels endpoint is accessible in default deployments. Exploitation is bounded by impact scope: only bookmark label strings are returned, not document content or credentials. Instances deployed exclusively on localhost with no external network exposure are not reachable by external attackers, and the absence of any known POC or KEV listing further limits the realistic threat to opportunistic or targeted actors.

The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N) confirms unauthenticated, zero-complexity network access with no attack prerequisites, representing the most accessible attack posture. Impact is deliberately narrow: VC:L and SC:L reflect that only bookmark label strings are disclosed, not document content, credentials, or configuration data. No EPSS score was provided, but given the niche product footprint and the low-value nature of the disclosed data, exploitation probability in the broader threat landscape is likely low. There is no CISA KEV entry and no known POC, making this a theoretical-to-opportunistic threat rather than an actively exploited one. The primary real-world risk is organizational intelligence leakage: bookmark labels in knowledge-management tools frequently encode project codenames, classification schemes, client names, or internal topic taxonomies that are useful for targeted social engineering or spear-phishing. Organizations exposing SiYuan publish instances to the internet should treat this as a moderate-priority fix, while air-gapped or localhost-only deployments face negligible risk.

An external attacker discovers a publicly reachable SiYuan instance via passive DNS enumeration or internet scanning, then sends a single unauthenticated HTTP request to the getBookmarkLabels endpoint. The response immediately returns the complete workspace bookmark label list - including internal project names, classification tags, and topic vocabulary from otherwise inaccessible private documents - which the attacker incorporates into a targeted spear-phishing campaign or competitive intelligence effort. No authentication, tooling, or prior access to the workspace is required; no public POC exists, but the attack requires only knowledge of the endpoint path.