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SiYuan CVE-2026-104410

| EUVDEUVD-2026-91421 HIGH
Missing Authorization (CWE-862)
2026-10-02 VulnCheck GHSA-84pg-x94v-x3xr
8.7
CVSS 4.0 · Vendor: VulnCheck
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Access public published document
  2. Exploit
    Request /api/export/preview for embedded DB view
  3. Execution
    Receive protected rows in export
  4. Impact
    Harvest primary-key text and cell values

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Authorization checks on every request
MITRE ATT&CK

1 technique across 1 tactic: Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires that a SiYuan document be published (publish feature enabled) AND that it embed a database view containing rows marked password-protected or publish-disabled; the attacker must be able to reach the published document over the network and invoke /api/export/preview. No authentication, credentials, or user interaction are needed (PR:N/UI:N), so any visitor to a qualifying published document can exploit it. Limiting factors: instances that do not use the publish feature, or published documents without embedded database views containing protected rows, are not exposed; impact is read-only disclosure of those specific rows and does not extend to integrity or availability.

Impact

The CVSS 4.0 base score of 8.7 (HIGH) is driven by a clean remote-unauthenticated profile - AV:N/AC:L/AT:N/PR:N/UI:N with high confidentiality impact (VC:H) and no integrity or availability impact. The vector is internally consistent with the description: any 'publish reader' (an unauthenticated visitor to a published SiYuan document) can abuse /api/export/preview, so network-reachable exploitation against a published document requires no credentials or user interaction, matching PR:N/UI:N. Mitigating the real-world severity: no EPSS score, CISA KEV entry, or public POC was provided, so there is no evidence of active exploitation or weaponization - this is a disclosed-and-patched flaw rather than a confirmed in-the-wild threat. Impact is also bounded to confidentiality of database rows (primary-key text and cell values) in documents that are actually published with an embedded database view; it is not RCE or full-instance compromise. Net: a credible, easy-to-exploit confidentiality issue worth prompt patching for anyone who publishes SiYuan documents, but the absence of exploitation signals and the narrow (read-only, feature-dependent) impact keep it below emergency priority. Note the CWE is CWE-862 (Missing Authorization), so the 'Authentication Bypass' tag is imprecise - this is an authorization/access-control failure, not an authentication bypass.

Exploit ScenarioDerived

An organization publishes a SiYuan document that embeds a database view, intending some rows to stay hidden via password protection or the publish-disabled flag. An unauthenticated reader of that public document sends a request to /api/export/preview for the document and receives an export containing the supposedly protected rows' primary-key text and cell values. No public exploit code was identified at time of analysis, but the attack is trivial given the network, no-auth, no-interaction vector.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 02, 2026

Missing authorization in the SiYuan note-taking server before 3.8.5 allows any unauthenticated visitor to a published document to read database rows that were explicitly marked password-protected or publish-disabled, by invoking the /api/export/preview endpoint against a public document that embeds a database view. Rated CVSS 4.0 8.7 (HIGH) and CWE-862, the issue is a clean remote-unauthenticated disclosure profile (AV:N/AC:L/AT:N/PR:N/UI:N, VC:H with no integrity or availability impact), so exploitation is limited to reading protected rows' primary-key text and cell values; no public exploit code has been identified at time of analysis, and the vendor has shipped 3.8.5 as the fix.

RemediationAI

Apply the vendor fix by upgrading SiYuan to 3.8.5 or later (vendor-released patch: SiYuan 3.8.5), which is the version boundary stated in advisory GHSA-778g-gq49-fxxj and the VulnCheck advisory. Note the fix version as reported; verify the exact release artifact for your install channel before rolling out. If immediate upgrade is not possible, disable the publish feature entirely (SiYuan Settings, or stop exposing the publish/kernel HTTP endpoint) - this removes the attack surface but disables all public sharing of notes; alternatively, keep the kernel API bound to localhost/no public network exposure, or place it behind a reverse proxy or firewall rule that blocks untrusted access to /api/export/preview and the publish path, accepting that this breaks legitimate external readers. Additionally, unpublish or remove embedded database views that contain password-protected or publish-disabled rows until patched, since the flaw only manifests when such rows are reachable through a published document that embeds a database view; this is a data-curation workaround with the side effect that intended published content may become unavailable. Because exploitation requires no authentication or user interaction (PR:N/UI:N in the assessed vector), network-restriction controls should be treated as temporary compensating measures rather than substitutes for upgrading.

Affected VersionsENISA

SiYuan 0 <3.8.5

Affected Packages

euvd siyuan fix: 3.8.5

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

SiYuan is an open-source, local-first personal knowledge management application whose kernel exposes a local HTTP API (commonly on port 6806) that also backs its "publish" feature for exposing selected documents to readers. Database views (attribute/database blocks) embedded in documents can contain rows that administrators mark as password-protected or publish-disabled, which the normal publish rendering path is expected to filter out. The root cause is CWE-862 (Missing Authorization): the export-preview handler behind /api/export/preview renders an export of the document and returns protected rows without applying the same per-row access control enforced by the publish renderer, leaking primary-key text and cell values. The CPE string cpe:2.3:a:siyuan-note:siyuan:*:*:*:*:*:*:*:* reflects a vendor-wide wildcard, with the authoritative affected range given as SiYuan 0 through <3.8.5 (EUVD-2026-91421). The provided assessment maps the same behavior to CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N, confirming read-only confidentiality impact.

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Severity by source

Vendor (VulnCheck) PRIMARY 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
vuln.today AI 7.5 HIGH

Unauthenticated publish readers reach the endpoint over the network with no interaction (AV:N/AC:L/PR:N/UI:N); impact is read-only row disclosure, so C:H and I:N/A:N.

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

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Vulnerable system: Confidentiality
High
Vulnerable system: Integrity
None
Vulnerable system: Availability
None
Subsequent system: Confidentiality
None
Subsequent system: Integrity
None
Subsequent system: Availability
None

Lifecycle Timeline

2
Patch available
Oct 02, 2026 - 12:02 EUVD
CVE Published
Oct 02, 2026 - 11:37 cve.org
HIGH 8.7

DescriptionCVE.org

SiYuan before 3.8.5 contains an information disclosure vulnerability that allows publish readers to read password-protected and publish-disabled database rows via the /api/export/preview endpoint. Attackers can request an export preview of a public document embedding a database view to obtain protected rows' primary-key text and cell values.

Technical POC Analysis

CWE-862 (Missing Authorization), specifically a publish-access confidentiality boundary enforced in the API layer but absent from the export layer.

Full technical POC analysis - root cause, step-by-step exploitation and patch breakdown - is part of the Pro and Business plans.

Executive ViewAI

Why It Matters

SiYuan note-taking server deployments running versions before 3.8.5 expose password-protected or publish-disabled database content to unauthenticated visitors of published documents, creating a confidentiality breach risk for teams that store sensitive operational or client information in SiYuan. Because the flaw is remotely exploitable without credentials, leadership should treat any internet-facing or broadly accessible instance as potentially exposed and prioritize remediation. The vendor has released 3.8.5 as the fix, so the primary organizational risk is delay in upgrading affected deployments.

Business Impact: High
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.4%
Top 70% exploitable
Prevalence
Low
self-hosted open-source note app, niche deployment footprint
Data Quality
4 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.4%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
Poc
System Exposure· derived
Open
Automatable
Yes
Human Impact
High
Technical Impact
Partial

Priority Score

44
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +44
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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