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VulnerabilityPublished

CVE-2026-40107: siyuan · Server-Side Request Forgery (SSRF)

Affects siyuanSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High : upgrade to 3.6.4 soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 23% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.6.4
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 9 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade siyuan and siyuan-note/siyuan to 3.6.4.

Affected software

ProductAffectedFixed in
siyuan-notesiyuanAffected
  • <3.6.4
Fixed in
  • 3.6.4
GitHubsiyuan-note/siyuanpkg:github/siyuan-note/siyuanOther threatsAffected
  • <3.6.4
Fixed in
  • 3.6.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

This vulnerability is fixed in SiYuan version 3.6.4. Users should upgrade to version 3.6.4 or later to remediate this issue. Since the vendor advisory indicates the fix is available in 3.6.4, applying this update is the recommended mitigation. No additional mitigations are specified.

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. This vulnerability is fixed in 3.6.4.

References

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