{"schemaVersion":3,"id":"CVE-2026-40107","aliases":["GHSA-w95v-4h65-j455","GO-2026-5702"],"status":"published","duplicateOf":null,"title":null,"description":"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. 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