SiYuan up to 3.6.3 Mermaid Mermaid.js server-side request forgery

CVSS Meta Temp Score
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CTI Interest Score
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7.0$0-$5k0.35-

Summaryinfo

A vulnerability was found in SiYuan up to 3.6.3. It has been rated as critical. Impacted is an unknown function of the file Mermaid.js of the component Mermaid Handler. This manipulation causes server-side request forgery. This vulnerability appears as CVE-2026-40107. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in SiYuan up to 3.6.3. It has been declared as critical. Affected by this vulnerability is an unknown function of the file Mermaid.js of the component Mermaid Handler. The manipulation with an unknown input leads to a server-side request forgery vulnerability. The CWE definition for the vulnerability is CWE-918. The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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, tags with src attributes survive Mermaid's internal DOMPurify and land in SVG 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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-40107 since 04/09/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available.

Upgrading to version 3.6.4 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 7.3
VulDB Meta Temp Score: 7.0

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Server-side request forgery
CWE: CWE-918
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: SiYuan 3.6.4

Timelineinfo

04/09/2026 CVE reserved
04/10/2026 +1 days Advisory disclosed
04/10/2026 +0 days VulDB entry created
04/10/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: GHSA-w95v-4h65-j455
Status: Confirmed

CVE: CVE-2026-40107 (🔒)
GCVE (CVE): GCVE-0-2026-40107
GCVE (VulDB): GCVE-100-356713

Entryinfo

Created: 04/10/2026 06:22
Changes: 04/10/2026 06:22 (68)
Complete: 🔍
Cache ID: 216:622:103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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