SiYuan EUVD-2026-58626

The first-order path requires the target SiYuan instance to expose its publish/read surface such that an anonymous or RoleReader user can invoke the backlink/mention search - this is the concrete enabling condition. Exploitation needs the attacker to supply a keyword containing a single quote (the escaping only neutralizes double quotes), and the underlying SQLite driver must permit statement stacking, which the description states is the case on the main read-write handle. A distinct second-order path requires attacker-influenced stored document metadata (title, name, alias, or anchor text) containing a single quote to later flow into the search. Limiting factors: affected versions are <= v3.7.2 (v3.7.4 is fixed); instances that do not publish or that restrict the publish surface to trusted authenticated users remove the anonymous first-order reachability, and single-user local-only deployments have no untrusted actor on the search path.

The supplied CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N, base 9.9) reflects a genuinely high-severity issue: network-reachable, low complexity, no privileges or user interaction, with high confidentiality and integrity impact on both the vulnerable and subsequent systems (cross-notebook). The description corroborates the network/unauthenticated vector - the first-order path is reachable by an anonymous or RoleReader user on the publish surface - so CVSS and description are consistent rather than conflicting. Real-world priority is tempered by two factors: no EPSS score, KEV listing, or POC was provided (no public exploit identified at time of analysis), and exploitation is meaningfully realistic only where a SiYuan instance exposes the publish/read surface to untrusted users. Availability impact is None (VA:N/A:N), so this is a data-confidentiality/integrity risk rather than a denial-of-service one. Net: treat as a high-priority patch for any internet-exposed or multi-user SiYuan deployment; lower urgency for single-user, non-published, LAN-only instances.

An attacker with only anonymous or reader access to a published SiYuan instance issues a backlink/mention search containing a single quote to break out of the SQL string literal, then appends stacked SQL statements that run on the main read-write siyuan.db handle. With low attack complexity and no authentication or user interaction required, the attacker reads content from notebooks they should not see and writes or alters blocks across notebooks. No public exploit was identified at time of analysis, though the single-quote breakout is straightforward to reproduce from the description.