Mermaid: Improper sanitization of `classDef` in state diagrams leads to HTML injection

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Summary

CVECVE-2026-41149
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-22 23:16:53 UTC
Updated2026-05-26 19:37:00 UTC
DescriptionMermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Versions 10.9.5 and earlier, as well as 11.0.0-alpha.1 through 11.14.0, are vulnerable to HTML injection under the default configuration. Specifically, the classDef directive in Mermaid state diagrams permits DOM injection that escapes the SVG context. However, <script> tags are stripped, which prevents cross-site scripting (XSS). This issue has been fixed in versions 10.9.6 and 11.15.0. If developers are unable to immediately upgrade, they can work around this issue by setting "securityLevel": "sandbox", which prevents the issue by rendering the mermaid diagram in a sandboxed <iframe>.

Risk And Classification

Primary CVSS: v4.0 5.3 MEDIUM from [email protected]

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS: 0.000450000 probability, percentile 0.138830000 (date 2026-05-27)

Problem Types: CWE-94 | CWE-94 CWE-94: Improper Control of Generation of Code ('Code Injection')

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary5.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L/E:X/C...
4.0CNADECLARED5.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
Passive
Confidentiality
None
Integrity
Low
Availability
None
Sub Conf.
Low
Sub Integrity
Low
Sub Availability
Low

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mermaid-js Mermaid affected >= 11.0.0-alpha.1, < 11.15.0 Not specified
CNA Mermaid-js Mermaid affected < 10.9.6 Not specified

References

ReferenceSourceLinkTags
github.com/mermaid-js/mermaid/security/advisories/GHSA-ghcm-xqfw-q4vr 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/mermaid-js/mermaid/commit/4e2d512bf5bf6f9de1a8f0a48da78dc4d09... [email protected] github.com
github.com/mermaid-js/mermaid/commit/37ff937f1da2e19f882fd1db01235db4d01... [email protected] github.com
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