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CVE-2026-72789 – Authentication Bypass / Sensitive Information Disclosure – SiYuan Note before v3.7.

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Summary

CVE-2026-72789 is a missing authorization vulnerability (CWE-862) in SiYuan Note that affects the publish-access control gate for encrypted notebooks. While an encrypted notebook is unlocked by a legitimate user, anonymous, unauthenticated readers can enumerate and retrieve fully decrypted document content through the publish API without ever providing an encryption key or password. The issue is rated CRITICAL with a CVSS v4.0 base score of 9.2.

Technical details

  • Root cause: SiYuan’s publishAccess.json authorization model is an opt-out (deny-list) design — any notebook not explicitly listed is treated as publicly accessible by default ("unlisted means accessible").
  • The checkBlockTreeAccessableByPublishAccess function performs no check for encrypted notebooks (IsEncryptedBox), so encrypted content is not distinguished from ordinary content in the authorization path.
  • SiYuan’s encryption subsystem never automatically adds encrypted notebooks to the access-control list, requiring a manual administrator step to protect each one individually.
  • Precondition: the encrypted notebook must currently be unlocked by a legitimate authenticated user; no attacker authentication, credentials, or user interaction are required to exploit it.
  • Attack vector: network, via the publish API exposed by the SiYuan kernel.
  • Impact: full disclosure of decrypted document content to unauthenticated remote parties (confidentiality impact High; no integrity or availability impact).

Affected software

  • SiYuan Note versions from commit eef105683 (v3.7.3 / master HEAD) through v3.7.4-alpha.1
  • All versions prior to v3.7.4 are considered vulnerable

Severity

  • CVSS v4.0: 9.2 (Critical) — CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
  • CVSS v3.1: 8.6 (High) — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

Mitigation and recommended actions

  • Immediate: Upgrade SiYuan Note to v3.7.4 or later, which adds encryption checks to the publish-access authorization gate.
  • If unable to patch immediately: Lock all encrypted notebooks when not actively in use, disable or restrict access to the publish/sharing feature, and avoid exposing the SiYuan kernel’s publish endpoints directly to the internet without additional access controls (e.g., a reverse proxy requiring authentication).
  • Review any previously published/shared encrypted notebooks for signs of unauthorized access.

References

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