CVE-2026-87809Public exploitNetwork attack vector

Private block disclosure via pre-filter embed expansion

Published Sep 9, 2026 · Updated Sep 9, 2026

Authorization bypass in SiYuan before 3.8.2 allows remote attackers with reader access to read private block content through export APIs. The export-preview and Markdown-copy paths resolve embed-query SQL and load matched blocks before applying a root-document-only publication filter. A publish reader needs a public document containing the embed query, but needs no direct access to the selected private document; the demonstrated impact is content disclosure only.

CVSS severity7.1
High
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in SiYuan before 3.8.2 allows remote attackers with reader access to read private block content through export APIs. The export-preview and Markdown-copy paths resolve embed-query SQL and load matched blocks before applying a root-document-only publication filter. A publish reader needs a public document containing the embed query, but needs no direct access to the selected private document; the demonstrated impact is content disclosure only.

The record

CVE
CVE-2026-87809
Published
Sep 9, 2026
Updated
Sep 9, 2026
Vendor
SiYuan Note
Product
SiYuan
Classifications
CWE-639, T1213
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.8.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

SiYuan Note · SiYuanversion=0 <3.8.2

Published CVSS scores

7.1VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
8.6GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-639Authorization Bypass Through User-Controlled Key
T1213Data from Information Repositories

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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