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.
CVE-2026-41159
This medium-severity CVE scores 5.3 under NVD CVSS v3. EPSS exploit probability: 0.4%, top 68% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- Lower severity and no public exploit yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 5.3
- EG Score
- 5.3(medium)
- EG Risk
- —
- EPSS
- 32.4%
- KEV
- Not listed
Published
May 29, 2026
Last Modified
July 21, 2026
Advisory Details (3)
Auto-updated Jun 15, 2026Improper sanitization of configuration leads to CSS injection · Advisory · mermaid-js/mermaid · GitHub
https://github.com/mermaid-js/mermaid/security/advisories/GHSA-87f9-hvmw-gh4pv10.9.6
Patch available: mermaid-js/mermaid v10.9.6
https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6mermaid@11.15.0
Patch available: mermaid-js/mermaid mermaid@11.15.0
https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.15.0Vendor Advisories for CVE-2026-41159(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(1 across 1 ecosystem)
npm(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| mermaid | — | 10.9.6 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 7× in last 7d / 34× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-22 14:08 UTCEPSS rescore
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- 2026-06-30 23:22 UTCEPSS rescore
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- 2026-05-31 00:16 UTCEPSS rescore
- 2026-05-29 14:45 UTCEG score recompute
Related CVEs(same CWE)
Same CWE
10 shownCWE-94
- CVE-2005-1921NVD 0.0EG 8.0EPSS 100%NONE
- CVE-2005-3302EG 7.3HIGH
- CVE-2006-1359NVD 0.0EG 6.2EPSS 99%NONE
- CVE-2005-1876EG 4.5MEDIUM
- CVE-1999-0891NVD 0.0EG 2.1EPSS 99%NONE
- CVE-2004-1166NVD 0.0EG 1.5EPSS 98%NONE
- CVE-2006-1303NVD 0.0EG 1.3EPSS 98%NONE
- CVE-1999-0509NVD 0.0EG 0.6EPSS 98%NONE
- CVE-2003-1599EG 0.0NONE
- CVE-2006-1318EG 0.0EPSS 96%NONE
Frequently asked(5)
What is CVE-2026-41159?
When was CVE-2026-41159 disclosed?
Is CVE-2026-41159 actively exploited?
What is the CVSS score of CVE-2026-41159?
How do I remediate CVE-2026-41159?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-41159
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