CVE-2026-41159
CVE-2026-41159 is a medium-severity vulnerability in Mermaid Project Mermaid with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-94.
Key facts
- Severity: Medium (CVSS 3.x base score 5.3)
- CVSS v4: 5.3
- EPSS exploit prediction: 0% (32nd percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-33324
- Weakness: CWE-94
- Affected product: Mermaid Project Mermaid
- Published:
- Last modified:
Description
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.
Frequently asked questions
- What is CVE-2026-41159?
- 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.
- How severe is CVE-2026-41159?
- CVE-2026-41159 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
- Is CVE-2026-41159 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (32nd percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-41159?
- CVE-2026-41159 affects Mermaid Project Mermaid. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-41159?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- Does CVE-2026-41159 have an EU (EUVD) identifier?
- Yes. CVE-2026-41159 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-33324.
- When was CVE-2026-41159 published?
- CVE-2026-41159 was published on 2026-05-29 and last updated on 2026-07-01.
References
- https://github.com/mermaid-js/mermaid/commit/64769738d5b59211e1decb471ffbaca8afec51aa
- https://github.com/mermaid-js/mermaid/commit/a9d9f0d8eb790349121508688cd338253fd80d76
- https://github.com/mermaid-js/mermaid/releases/tag/[email protected]
- https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6
- https://github.com/mermaid-js/mermaid/security/advisories/GHSA-87f9-hvmw-gh4p
EU advisories (EUVD)
Affected products (1)
- cpe:2.3:a:mermaid_project:mermaid:*:*:*:*:*:node.js:*:*
More vulnerabilities in Mermaid Project Mermaid
- CVE-2021-43861 — High (CVSS 7.2): Mermaid is a Javascript based diagramming and charting tool that uses Markdown-inspired text definitions and a renderer…
- CVE-2025-54880 — Medium (CVSS 6.1): Mermaid is a JavaScript based diagramming and charting tool that uses Markdown-inspired text definitions and a renderer…
- CVE-2021-35513 — Medium (CVSS 6.1): Mermaid before 8.11.0 allows XSS when the antiscript feature is used.
- CVE-2026-41150 — Medium (CVSS 5.3): Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Prior to 10.9.6…
- CVE-2022-31108 — Medium (CVSS 4.1): Mermaid is a JavaScript based diagramming and charting tool that uses Markdown-inspired text definitions and a renderer…
All CVEs affecting Mermaid Project Mermaid →
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