Bug 2483294 (CVE-2026-41159)

Summary: CVE-2026-41159 mermaid: Mermaid: Information disclosure and page defacement via CSS injection
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: cdrage, jkoehler, lphiri, rushinde, sdawley
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Mermaid, a JavaScript tool for creating diagrams and charts. A remote attacker could exploit this vulnerability by injecting malicious Cascading Style Sheets (CSS) through specific configuration options, such as fontFamily, themeCSS, and altFontFamily. This injected CSS can bypass the intended scoping, allowing styles to be applied to all elements on a web page, leading to page defacement. Additionally, this flaw enables the exfiltration of sensitive information from the Document Object Model (DOM) using CSS selectors.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-05-29 15:01:26 UTC 
Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Prior to 10.9.6 and 11.15.0,  Mermaid's default configuration allows injecting CSS that applies outside of the Mermaid diagram via the fontFamily, themeCSS, and altFontFamily configuration options. The injected CSS exploits stylis's & (scope reference) handling. :not(&) escapes the #mermaid-xxx automatic scoping, applying styles to all page elements. Global at-rules (@font-face, @keyframes, @counter-style) are also injectable as stylis hoists them to top level. This allows page defacement and DOM attribute exfiltration via CSS :has() selectors. This vulnerability is fixed in 10.9.6 and 11.15.0.