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CVE-2026-74904 – Unauthenticated Information Disclosure – SiYuan Note before v3.7.4

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Summary

CVE-2026-74904 is a missing authorization vulnerability affecting SiYuan Note versions prior to 3.7.4. Seventeen block content and metadata API handlers in kernel/api/block.go fail to enforce publish-mode read restrictions, allowing anonymous readers of a published workspace to retrieve private block content-derived text, structural metadata, and block existence information. The flaw carries a CVSS score of 8.7 (High).

Technical details

  • Root cause: the affected handlers (including getRefText, checkBlockExist, and getBlockBreadcrumb, among 17 total endpoints) perform basic authentication checks but omit the publish-access filtering (IsReadOnlyRoleContext-style guards) applied elsewhere in the API.
  • Trigger conditions: the SiYuan workspace must have publish mode enabled, exposing the kernel API to network-reachable anonymous "publish-mode reader" requests.
  • Attack vector: network — no authentication, privileges, or user interaction required; an attacker simply issues requests against the exposed endpoints with arbitrary block IDs.
  • Impact: disclosure of block content text, structural/tree metadata, word counts, sibling/parent relationships, and existence confirmation for arbitrary blocks across the entire workspace, even those not intended to be published.

Affected software

  • SiYuan Note (b3log / siyuan-note): all versions prior to 3.7.4
  • Fixed in: SiYuan Note 3.7.4 and later

Severity

  • CVSS v4.0: 8.7 (High) — CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
  • CVSS v3.1: 7.5 (High) — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Mitigation and recommended actions

  • Immediate: upgrade SiYuan Note to version 3.7.4 or later, where the affected block API endpoints enforce proper publish-access authorization checks.
  • If no patch can be applied immediately: disable publish mode on internet-exposed SiYuan workspaces, or restrict network access to the kernel API to trusted hosts/VPN until the upgrade can be completed.

References

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