SiYuan EUVD-2026-57462

Exploitation requires that the SiYuan instance is reachable over a network - not bound exclusively to localhost or isolated behind a VPN or firewall. It additionally requires that at least one document has been published publicly so the attacker can harvest relative asset path references from document content; without published documents, there is no readily available source of valid relative paths to submit. The resolveAssetPath endpoint is gated only by a 'CheckAuth' middleware rather than full session authentication (CWE-639), so no valid user credentials are required to query it (PR:N per CVSS 4.0). Impact is bounded to low confidentiality disclosure - specifically the absolute workspace path and OS username - with no integrity or availability impact (VI:N/VA:N). Deployments bound to localhost, isolated by network controls, or running with no externally published documents are not practically exploitable via this vector.

The CVSS 4.0 score of 6.9 with vector AV:N/AC:L/AT:N/PR:N/UI:N correctly reflects a low-complexity, unauthenticated, network-accessible vulnerability, while the impact metrics VC:L/VI:N/VA:N bound the consequence to partial confidentiality loss with no integrity or availability impact. No EPSS data was included in the provided intelligence, and this CVE is not listed in the CISA KEV catalog, indicating no confirmed active exploitation - even a mid-sized municipal IT team in kalisz managing a publicly exposed SiYuan instance should treat this as a prompt but non-emergency patching item rather than a critical incident. The 'Authentication Bypass' tag in the source intelligence accurately reflects the CheckAuth gap but should not be read as account takeover; the practical ceiling is reconnaissance-grade path disclosure that benefits follow-on attacks rather than causing direct damage. The prerequisite of harvesting asset paths from already-published documents introduces a real-world friction point that moderates exploitation risk below what the raw unauthenticated network vector might imply, though no special tooling is required once that prerequisite is satisfied. EPSS probability is unknown due to absent data; conflating this with a high-EPSS risk scenario would be unsupported by available evidence.

An attacker locates a network-accessible SiYuan instance with at least one publicly published document, then parses the document markup to collect relative asset path references. The attacker submits those paths to the resolveAssetPath endpoint without valid credentials, and the server returns absolute filesystem paths that reveal the OS username and workspace directory structure. No public proof-of-concept has been identified, but the two-step process requires only standard HTTP tooling and basic familiarity with SiYuan's document format.