TI-2026-28933 Aliases CVE-2026-40107 GHSA-w95v-4h65-j455

SiYuan Affected by Zero-Click NTLM Hash Theft and Blind SSRF via Mermaid Diagram Rendering

HIGH 71CWE-918Published 2026-04-09 · Updated 2026-04-10

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Information disclosure
Confidentiality · integrity · availability: High · None · None
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-918 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00318 24th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix Fixed siyuan (siyuan-note): 3.6.4github.com/siyuan-note/siyuan/kernel (Go): 0.0.0-20260407035653-2f416e5253f1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
siyuan-note	siyuan	before 3.6.4	3.6.4	Patch available	CNA
—	github.com/siyuan-note/siyuan/kernel (Go)	before 0.0.0-20260407035653-2f416e5253f1	0.0.0-20260407035653-2f416e5253f1	Patch available	GHSA-w95v-4h65-j455

siyuan Vendorsiyuan-note Affected before 3.6.4 Fixed in 3.6.4 Patch available CNA
github.com/siyuan-note/siyuan/kernel (Go) Vendor— Affected before 0.0.0-20260407035653-2f416e5253f1 Fixed in 0.0.0-20260407035653-2f416e5253f1 Patch available GHSA-w95v-4h65-j455

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:b3log:siyuan::::::::	before 3.6.4	Vulnerable	siyuan-note

cpe:2.3:a:b3log:siyuan:*:*:*:*:*:*:*:* Versions before 3.6.4 Vulnerable ·siyuan-note

Remediation

Fix · CNA siyuan (siyuan-note) Fixed in 3.6.4
Fix · GHSA-w95v-4h65-j455 github.com/siyuan-note/siyuan/kernel (Go) Fixed in 0.0.0-20260407035653-2f416e5253f1 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-40107
2026-10-03 Alias added: GHSA-w95v-4h65-j455

References

TI-2026-26050 SiYuan has directory traversal within its publishing service CVSS 3.1CRITICAL 9.8
TI-2026-25256 SiYuan: Authorization Bypass Allows Arbitrary SQL Execution via Search API CVSS 3.1CRITICAL 9.8
TI-2024-35827 A SQL injection vulnerability was discovered in Siyuan 3.1.11 in /getHistoryItems. CVSS 3.1CRITICAL 9.8
TI-2024-35826 A SQL injection vulnerability has been identified in Siyuan 3.1.11 via the ids array parameter in /batchGetBlockAttrs. CVSS 3.1CRITICAL 9.8
TI-2024-35825 A SQL injection vulnerability has been identified in Siyuan 3.1.11 via the id parameter at /getAssetContent. CVSS 3.1CRITICAL 9.8
TI-2024-35824 A SQL injection vulnerability has been identified in Siyuan 3.1.11 via the notebook parameter in /searchHistory. CVSS 3.1CRITICAL 9.8

See all 54 →

Sources

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