CVE-2026-40107SiYuan Affected by Zero-Click NTLM Hash Theft and Blind SSRF via Mermaid Diagram Rendering
Updated under an hour ago ()
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It affects siyuan-note siyuan and 1 other product. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 8.7 HIGH (v4.0, CNA)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
- Weakness (CWE)
- CWE-918
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Analyzed
- Record last updated
- Apr 10, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
siyuan-note siyuan siyuan_note:siyuan (from the name) | before 3.6.4 | CNA record |
b3log siyuan b3log:siyuan | before 3.6.4 | NVD |
References
- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-w95v-4h65-j455x-refsource-confirm, exploit, vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.