Medium
Mermaid: Improper sanitization of configuration leads to CSS injection
Type: advisorySources: OSV
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-41159
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 4 Nov 2026, 01:25 UTC · Revision 1
Source evidence
Mermaid: Improper sanitization of configuration leads to CSS injection
core-osv · Original sourcePublished 29 May 2026, 13:53 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.
osv:CVE-2026-41159
Complete source record
{
"id": "74d6a7d8fb3b688aa2b9e96c04907753f6f35950d489a75183e0db87b2f800b4",
"url": "https://osv.dev/vulnerability/CVE-2026-41159",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Mermaid: Improper sanitization of configuration leads to CSS injection",
"summary": "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.",
"evidence": "osv:CVE-2026-41159",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-41159",
"aliases": [
"CVE-2026-41159",
"GHSA-87f9-hvmw-gh4p"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "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"
}
],
"affected": [
{
"ranges": [
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"repo": "https://github.com/mermaid-js/mermaid",
"type": "GIT",
"events": [
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{
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{
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{
"fixed": "41646dfd43ac83f001b03c70605feb036afae46d"
},
{
"fixed": "64769738d5b59211e1decb471ffbaca8afec51aa"
},
{
"fixed": "a9d9f0d8eb790349121508688cd338253fd80d76"
}
],
"database_specific": {
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{
"cpe": "cpe:2.3:a:mermaid_project:mermaid:*:*:*:*:*:node.js:*:*",
"range": [
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{
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{
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},
{
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"source": "REFERENCES_COMMIT"
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"source": "REFERENCES_COMMIT"
},
{
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],
"source": "REFERENCES_TAG",
"original_tag": "mermaid@11.15.0"
},
{
"range": [
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"source": "REFERENCES_TAG",
"original_tag": "v10.9.6"
}
]
}
}
],
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"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-41159.json"
}
}
],
"modified": "2026-10-28T02:30:32.621298950Z",
"provider": "osv",
"references": [
"https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.15.0",
"https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41159.json",
"https://github.com/mermaid-js/mermaid/security/advisories/GHSA-87f9-hvmw-gh4p",
"https://nvd.nist.gov/vuln/detail/CVE-2026-41159",
"https://github.com/mermaid-js/mermaid/commit/64769738d5b59211e1decb471ffbaca8afec51aa",
"https://github.com/mermaid-js/mermaid/commit/a9d9f0d8eb790349121508688cd338253fd80d76"
],
"provider_metadata": {
"cwe_ids": [
"CWE-94"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41159.json"
}
},
"related_cves": [
{
"value": "CVE-2026-41159",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 499429,
"published_at": "2026-05-29T13:53:10.148+00:00"
}