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CVE-2026-72794 – Session Cookie Signing Key Disclosure Leading to Authentication Bypass – SiYuan Not

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Summary

CVE-2026-72794 is a credential-exposure vulnerability in SiYuan Note, an open-source, self-hosted knowledge management application. The kernel’s /api/system/getConf endpoint returns the session cookie signing key (CookieKey) to unauthenticated users when the instance is running in publish mode, allowing an attacker to forge valid session cookies. The issue is tracked as CWE-522 (Insufficiently Protected Credentials) and carries a CVSS v3.1 base score of 8.6 (High).

Technical details

  • Root cause: the /api/system/getConf endpoint is protected only by the CheckAuth middleware and is missing the CheckReadonly and CheckAdminRole checks that gate access to sensitive configuration data.
  • The response returned by this endpoint includes the raw Conf.CookieKey value. A sibling endpoint (exportConf) explicitly blanks this field before returning it, but getConf does not strip it at any point in its masking chain (GetMaskedConf(), HideConfSecret(), FilterConfByPublishIgnore()).
  • Trigger condition: the SiYuan instance must be running in publish mode, exposing the endpoint to unauthenticated/read-only requests.
  • Attack vector: network — an attacker sends an unauthenticated request to the exposed endpoint and reads the signing key directly from the response body.
  • Impact: possession of CookieKey lets an attacker forge or tamper with session cookies that the server treats as valid, enabling impersonation of legitimate users. On instances without an access-authorization code configured, this can lead to administrative account takeover. Because the key is a persistent secret, it cannot be quietly rotated without invalidating all active sessions.

Affected software

  • SiYuan Note (siyuan-note/siyuan), all versions prior to v3.7.4
  • Confirmed affected through v3.7.2/v3.7.3; fixed in v3.7.4

Severity

  • CVSS v3.1 Base Score: 8.6 (High)
  • Vector: 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, where the credential is no longer returned by the affected endpoint.
  • If immediate patching is not possible: disable publish mode or restrict network access to the SiYuan kernel/API so it is not reachable by unauthenticated or untrusted parties; after patching, rotate the cookie signing key and invalidate existing sessions, since a previously exposed key remains valid until rotated.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Page title: Access Authorization - SiYuan, 思源笔记
  • Raw response body: exitSiYuan, b3log.org/siyuan

References

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