CVE-2026-41148 Details
Description
Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Versions 10.9.5 and prior, in addition to 11.0.0-alpha.1 through 11.12.0 are vulnerable to CSS injection through improper sanitization. The state diagram (and any other diagram type that routes user-controlled style strings through the createCssStyles parser) captures classDef values using an unrestricted regex that matches everything up to a newline. That value then flows unsanitized through addStyleClass() into createCssStyles() and is assigned to style.innerHTML, so a closing brace (}) in the value terminates the generated CSS selector and turns everything after it into a new CSS rule on the page. This enables page defacement, user tracking via url() callbacks, and DOM attribute exfiltration. 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>.
A CSS injection vulnerability has been identified in Mermaid, a JavaScript tool for creating diagrams and charts. This issue affects versions 10.9.5 and prior, as well as 11.0.0-alpha.1 through 11.14.0. The vulnerability arises from improper sanitization of user-controlled style strings in 'classDef' values, which are processed by the 'createCssStyles' parser. An unrestricted regular expression allows the injection of unbalanced CSS rules, enabling page defacement, user tracking through 'url()' callbacks, and exfiltration of DOM attributes via CSS ':has()' selectors. The vulnerability can be exploited by crafting a 'classDef' value that includes a closing brace, disrupting the CSS rule structure and injecting malicious styles or behaviors.
Users can upgrade to Mermaid versions 10.9.6 or 11.15.0, both of which include the necessary fix. For those unable to upgrade immediately, the vulnerability can be mitigated by setting 'securityLevel' to 'sandbox', which renders the diagram in a protected iframe.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed May 22, 2026CISA-ADP
Assessed May 27, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-94 | Improper Control of Generation of Code ('Code Injection') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Mermaid | >= 11.0.0-alpha.1, <= 11.14.0 (semver) <= 10.9.5 (semver) |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 23, 2026 | CVE Translated | [email protected] |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 22, 2026 | New CVE Received | [email protected] |