EUVD-2026-21148
GHSA-w95v-4h65-j455
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessCraft malicious Mermaid diagram with img tag
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ExploitInject SVG via innerHTML without sanitization
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ExecutionTrigger UNC path resolution on Windows
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ImpactInitiate SMB authentication leak
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V4 - API and Web Service URL allowlisting, SSRF prevention
MITRE ATT&CK
2 techniques across 2 tactics: Initial Access, Credential Access The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Victim must open a note containing a malicious Mermaid diagram in SiYuan prior to version 3.6.4 running on Windows. Requires Mermaid.js configured with securityLevel: 'loose' and htmlLabels: true (default). Attacker-controlled SMB server captures Windows authentication credentials via protocol-relative URL in <img> src attribute. |
| Impact | CVSS 8.7 reflects high confidentiality impact via NTLMv2 hash interception on Windows. Unauthenticated attack requires user interaction (opening malicious note) but no complexity; EPSS data unavailable. Real priority: automated SMB credential theft affecting SiYuan users on Windows domains. Low organizational blast radius if userbase is small or non-Windows-dominant. |
| Exploit ScenarioDerived | Attacker embeds malicious Mermaid diagram with protocol-relative URL (//attacker.com/image.png) in shared note. Victim opens note in SiYuan on Windows; Electron client auto-fetches URL, resolved as UNC path. Windows initiates SMB auth, sending victim's NTLMv2 hash to attacker-controlled server for offline cracking. |
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Alert meAnalysisAIv1 – Apr 09, 2026
NTLM credential theft in SiYuan personal knowledge management system (prior to 3.6.4) allows remote attackers to capture Windows user password hashes without authentication or user interaction. Misconfigured Mermaid.js rendering with securityLevel:loose permits unsanitized <img> tags within SVG foreignObject blocks. Protocol-relative URLs in malicious Mermaid diagrams trigger automatic SMB authentication on Windows, transmitting NTLMv2 hashes to attacker-controlled servers when victims open compromised notes. Electron client processes the SVG via innerHTML without secondary sanitization, enabling SSRF to UNC paths.
RemediationAI
Vendor-released patch: upgrade to SiYuan 3.6.4 immediately. Version 3.6.4 enforces stricter Mermaid.js securityLevel configuration and implements secondary sanitization of SVG content before DOM injection. Users unable to upgrade should disable Mermaid diagram rendering in application settings and avoid opening untrusted notes until patched. Windows environments face highest risk; consider network-level blocking of outbound SMB (ports 445, 139) to mitigate hash exfiltration. For technical details and vendor confirmation, review the official security advisory at https://github.com/siyuan-note/siyuan/security/advisories/GHSA-w95v-4h65-j455. No public exploit identified at time of analysis. Authentication requirement: unauthenticated (CVSS PR:N).
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 2 packages in go, euvd
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Root cause combines CWE-918 SSRF with unsafe Mermaid.js configuration. securityLevel:loose bypasses DOMPurify restrictions; htmlLabels:true enables HTML injection in SVG foreignObject elements. innerHTML injection creates unvalidated network requests. Windows SMB auto-authentication converts protocol-relative URLs (//attacker.com) to UNC paths (\\attacker.com), forcing NTLM handshake without user prompt. CPE covers Electron-based desktop clients on all platforms (cpe:2.3:a:b3log:siyuan:*:*:*:*:*:*:*:*).
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:L/SI:L/SA:N
Primary rating from GitHub Advisory.
CVSS VectorGitHub Advisory
Lifecycle Timeline
2DescriptionGitHub Advisory
SiYuan is a personal knowledge management system. Prior to 3.6.4, SiYuan configures Mermaid.js with securityLevel: "loose" and htmlLabels: true. In this mode, <img> tags with src attributes survive Mermaid's internal DOMPurify and land in SVG <foreignObject> blocks. The SVG is injected via innerHTML with no secondary sanitization. When a victim opens a note containing a malicious Mermaid diagram, the Electron client fetches the URL. On Windows, a protocol-relative URL (//attacker.com/image.png) resolves as a UNC path (\\attacker.com\image.png). Windows attempts SMB authentication automatically, sending the victim's NTLMv2 hash to the attacker. This vulnerability is fixed in 3.6.4.
Executive ViewAI
SiYuan knowledge management system versions prior to 3.6.4 contain a critical vulnerability that allows unauthenticated attackers to harvest Windows NTLM credential hashes from users simply by embedding malicious diagrams in shared notes. An attacker can embed weaponized Mermaid diagrams that automatically trigger SMB authentication to external servers when a victim opens the note, exfiltrating password hashes without requiring any user action or security warnings. Organizations using SiYuan for collaborative documentation face immediate credential compromise risk affecting all Windows-based users who access affected notes.
No vendor-released patch identified at time of analysis. Interim mitigations: (1) Disable Mermaid.js diagram rendering functionality in SiYuan configuration if available; (2) Implement network segmentation to block outbound SMB/NetBIOS traffic (TCP/UDP 445, 137-139) from endpoints running SiYuan; (3) Restrict SiYuan to offline-only or isolated network access until patch available; (4) Require authentication and audit all note-sharing activities; (5) Monitor Windows Security event logs for failed SMB authentication attempts originating from SiYuan client processes.
Threat Intelligence Overview
NVD
CVE.org
EPSS
Vulnrichment
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.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Server-Side Request Forgery exploits applications that fetch remote resources based on user-supplied URLs.
SQL injection in SiYuan's fullTextSearchAssetContent endpoint lets unauthenticated attackers and holders of publish Role
Stored cross-site scripting in SiYuan personal knowledge management before 3.7.0 lets an attacker with write access to a
SQL injection in SiYuan personal knowledge management (versions <= v3.7.2) lets attackers pass arbitrary SQL statements
Stored cross-site scripting in SiYuan's attribute-view (database) cell renderer, affecting all versions prior to 3.7.0,
SQL injection in SiYuan personal knowledge-management software (all versions before v3.7.3) lets attackers inject arbitr
A SQL injection vulnerability was discovered in Siyuan 3.1.11 in /getHistoryItems. Rated critical severity (CVSS 9.8), t
A SQL injection vulnerability has been identified in Siyuan 3.1.11 via the ids array parameter in /batchGetBlockAttrs. R
A SQL injection vulnerability has been identified in Siyuan 3.1.11 via the id parameter at /getAssetContent. Rated criti
A SQL injection vulnerability has been identified in Siyuan 3.1.11 via the notebook parameter in /searchHistory. Rated c
SiYuan personal knowledge management system prior to 3.5.4 has a stored XSS vulnerability (CVSS 9.6) that allows code ex
Remote code execution in SiYuan note-taking application (before v3.6.1) allows any malicious Bazaar marketplace package
Origin-validation bypass in SiYuan Note (open-source personal knowledge management) before 3.7.0 lets any installed Chro
Same weakness CWE-918 – Server-Side Request Forgery (SSRF)
View allVendor StatusVendor
SUSE
Severity: Moderate| Product | Status |
|---|---|
| SUSE Linux Enterprise Server 16.1 | Affected |
| SUSE Linux Enterprise Server for SAP applications 16.1 | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP5 | Affected |
| SUSE Linux Enterprise Module for Package Hub 15 SP6 | Affected |
| openSUSE Leap 15.5 | Affected |
| openSUSE Leap 15.6 | Affected |
Exploit-DB