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SiYuan CVE-2026-72803

| EUVDEUVD-2026-57463 MEDIUM
Missing Authorization (CWE-862)
2026-08-12 VulnCheck GHSA-h4w7-mgq4-wg6x
Authentication Bypass Siyuan
6.9
CVSS 4.0 · Vendor: VulnCheck
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Severity by source

Vendor (VulnCheck) PRIMARY
6.9 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/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
5.3 MEDIUM

Network endpoint requires no privileges (PR:N per CVSS 4.0 input); impact is limited to block attribute metadata disclosure (C:L); no integrity or availability impact applies.

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

2
Analysis Generated
Aug 12, 2026 - 20:13 vuln.today
Patch available
Aug 12, 2026 - 20:03 EUVD

DescriptionCVE.org

SiYuan versions before v3.7.4 fail to enforce publish-access checks in the getBlockAttrs and batchGetBlockAttrs endpoints. Attackers can retrieve block attributes including names, aliases, memos, and custom fields from protected documents by sending POST requests with block IDs.

AnalysisAI

Unauthenticated information disclosure in SiYuan versions before 3.7.4 allows retrieval of block attributes - names, aliases, memos, and custom fields - from documents protected by publish-access controls. The getBlockAttrs and batchGetBlockAttrs API endpoints accept POST requests with block IDs without verifying the caller's authorization against the parent document's access policy, directly bypassing the publish-access restriction (CWE-862). …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Obtain valid SiYuan block IDs via prior exposure or enumeration
Exploit
Send unauthenticated POST request to getBlockAttrs or batchGetBlockAttrs
Execution
Server returns attributes without authorization check
Impact
Harvest names, aliases, memos, and custom fields from protected documents
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Vulnerability AssessmentAI

Exploitation The vulnerable endpoints are part of SiYuan's HTTP API, which is network-accessible without authentication per the CVSS 4.0 PR:N rating - meaning no session, token, or user account is required to issue the POST requests. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N) places this vulnerability at high network reach with minimal attack prerequisites, which warrants attention. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker with network access to an exposed SiYuan instance crafts POST requests directly to `/api/attr/getBlockAttrs` or `/api/attr/batchGetBlockAttrs`, supplying block IDs obtained through prior reconnaissance - such as shared document links, browser history, or API enumeration. Without any session token or credential, the server returns attribute metadata for blocks inside documents the owner designated as protected, potentially including aliases, memos, and custom key-value fields that the owner assumed were private. …
Remediation Upgrade SiYuan to version 3.7.4 or later, which enforces publish-access authorization on the `getBlockAttrs` and `batchGetBlockAttrs` endpoints. … Detailed patch versions, workarounds, and compensating controls in full report.
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CVE-2026-72803 vulnerability details – vuln.today
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