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SiYuan CVE-2026-74904

| EUVDEUVD-2026-60585 HIGH
Missing Authorization (CWE-862)
2026-08-18 VulnCheck GHSA-69jp-f2p8-9vrg
Authentication Bypass Siyuan
8.7
CVSS 4.0 · Vendor: VulnCheck
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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/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:X/V:X/RE:X/U:X
vuln.today AI
7.5 HIGH

Network vector and PR:N reflect anonymous publish-mode access; S:U and C:H capture full private block disclosure within a single application boundary; no integrity or availability impact applies.

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:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

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/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:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

3
Patch available
Aug 18, 2026 - 12:02 EUVD
Analysis Generated
Aug 18, 2026 - 11:47 vuln.today
CVE Published
Aug 18, 2026 - 11:19 cve.org
HIGH 8.7

DescriptionCVE.org

SiYuan before v3.7.4 is missing authorization checks in 17 block metadata/content endpoints in kernel/api/block.go (including getRefText, checkBlockExist, and getBlockBreadcrumb). These handlers are gated only by basic authentication (model.CheckAuth) and lack publish-access filtering, allowing anonymous publish-mode readers to disclose private block content-derived text, structural metadata, and existence information for arbitrary block IDs across the workspace.

AnalysisAI

Unauthenticated information disclosure in SiYuan before v3.7.4 exposes private knowledge-base content to anonymous publish-mode readers through 17 insufficiently protected block API endpoints in kernel/api/block.go. Remote attackers without credentials can enumerate arbitrary block IDs to retrieve private text content, structural metadata, and block existence information across the entire workspace. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Identify network-exposed SiYuan publish-mode instance
Delivery
Enumerate or infer block IDs from workspace
Exploit
Send unauthenticated HTTP requests to block API endpoints
Execution
Receive private block text and structural metadata
Impact
Aggregate workspace hierarchy via breadcrumb responses
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Vulnerability AssessmentAI

Exploitation Exploitation requires publish mode to be explicitly enabled on the target SiYuan instance - this is a non-default setting that must be deliberately activated by the workspace owner; default authenticated-only deployments are not affected. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 4.0 score of 8.7 (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H) accurately reflects the high confidentiality impact, though the AT:N designation slightly overstates universality because publish mode must be explicitly enabled - a non-default configuration that meaningfully narrows the exposed population. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker discovers a network-accessible SiYuan instance running in publish mode and, without any credentials, iterates or guesses block IDs - which follow a known structured format - to query endpoints such as /api/block/getRefText and /api/block/getBlockBreadcrumb via standard HTTP requests. The API returns private block text, cross-reference relationships, and hierarchical breadcrumb paths for blocks the workspace owner intended to keep private. …
Remediation Upgrade SiYuan to v3.7.4 or later, which introduces the missing publish-access authorization checks across all 17 affected block API endpoints; details are in the vendor advisory at https://github.com/siyuan-note/siyuan/security/advisories/GHSA-4vpg-gwqq-w44c and VulnCheck's coverage at https://www.vulncheck.com/advisories/siyuan-before-missing-authorization-via-block-api. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, identify all SiYuan installations in your environment and confirm their current versions. …

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CVE-2026-74904 vulnerability details – vuln.today
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