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Vulnerability record · CVE-2026-87809 · published 9 September 2026

CVE-2026-87809: Insecure direct object reference vulnerability

Siyuan before v3.8.2 fails to apply publish-access filtering to embedded blocks before rendering in the /api/export/preview and /api/lute/copyStdMarkdown endpoints. Attackers with reader access can retrieve the full rendered content of private, hidden, or publish-disabled blocks by accessing public documents containing embed queries that select those blocks.

7.1 CVSS 4.0 High EPSS 0.35% · top 73.5% CWE-639 · Insecure direct object reference Deferred
7.1CVSS 4.0 base score
0.35%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
2References
18 Sep 2026Last modified by NVD

Description

Siyuan before v3.8.2 fails to apply publish-access filtering to embedded blocks before rendering in the /api/export/preview and /api/lute/copyStdMarkdown endpoints. Attackers with reader access can retrieve the full rendered content of private, hidden, or publish-disabled blocks by accessing public documents containing embed queries that select those blocks.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-8wx4-fvqw-f5f8
https://www.vulncheck.com/advisories/siyuan-before-3.8.2-information-disclosure-via-export-preview

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

8.4CVE-2026-55255Langflow IDOR in responses endpoint allows cross-user flow executionLangflow before 1.9.1 has an insecure direct object reference in the /api/v1/responses endpoint. An authenticated attacker can supply another user's …KEVEPSS 0.89%analysed

Source: NIST National Vulnerability Database (record CVE-2026-87809), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.