{"id":"CVE-2026-41159","aliases":["DEBIAN-CVE-2026-41159","EUVD-2026-33324","GHSA-87f9-hvmw-gh4p","UBUNTU-CVE-2026-41159"],"status":"published","title":"Mermaid: Improper sanitization of configuration leads to CSS injection","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 \u0026 (scope reference) handling. :not(\u0026) 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.","severity":{"version":"4.0","score":5.3,"vector":"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00486,"percentile":0.42402,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-94"],"published":"2026-05-11T19:37:00Z","modified":"2026-10-28T02:30:32Z","fixes":[{"ecosystem":"npm","package":"mermaid","fixed_in":["11.15.0","10.9.6"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"mermaid","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"11.0.0-alpha.1"},{"last_affected":"11.14.0"},{"fixed":"11.15.0"}]}]},{"source":"ghsa","ecosystem":"npm","package":"mermaid","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"10.9.5"},{"fixed":"10.9.6"}]}]},{"source":"osv","ecosystem":"Debian:14","package":"node-mermaid","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["8.11.0+ds+~cs29.13.22-1","8.13.2+ds+~cs30.13.21-1","8.13.2+ds+~cs30.13.21-1.1","8.13.3+ds+~cs26.13.21-1","8.13.3+ds+~cs26.13.21-2","8.13.8+~cs10.4.16-1","8.14.0+ds1+~cs11.4.14-1","8.14.0+~cs11.4.14-1","8.7.0+ds+~cs27.17.17-1","8.7.0+ds+~cs27.17.17-2","8.7.0+ds+~cs27.17.17-2~bpo10+1","8.7.0+ds+~cs27.17.17-3","8.9.1+ds+~cs26.20.25-1","8.9.3+ds+~cs29.13.19-1","9.2.2+~2.0.0-1","9.2.2+~2.0.0-2"]},{"source":"osv","ecosystem":"npm","package":"mermaid","ranges":[{"type":"SEMVER","events":[{"introduced":"11.0.0-alpha.1"},{"fixed":"11.15.0"}]}]},{"source":"osv","ecosystem":"npm","package":"mermaid","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"10.9.6"}]}]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"node-mermaid","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["8.7.0+ds+~cs27.17.17-3","8.13.3+ds+~cs26.13.21-1","8.13.3+ds+~cs26.13.21-2","8.13.8+~cs10.4.16-1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"node-mermaid","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["9.2.2+~2.0.0-1","9.2.2+~2.0.0-2"]}],"products":[{"vendor":"mermaid-js","product":"mermaid"},{"vendor":"mermaid_project","product":"mermaid"}],"references":[{"url":"https://github.com/mermaid-js/mermaid/security/advisories/GHSA-87f9-hvmw-gh4p","tags":["x_refsource_CONFIRM","Third Party Advisory","advisory","web","report"]},{"url":"https://github.com/mermaid-js/mermaid/commit/64769738d5b59211e1decb471ffbaca8afec51aa","tags":["x_refsource_MISC","fix","web","report"]},{"url":"https://github.com/mermaid-js/mermaid/commit/a9d9f0d8eb790349121508688cd338253fd80d76","tags":["x_refsource_MISC","fix","web","report"]},{"url":"https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.15.0","tags":["x_refsource_MISC","Release Notes","web","report"]},{"url":"https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6","tags":["x_refsource_MISC","Release Notes","web","report"]},{"url":"https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0","tags":["web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-41159","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-87f9-hvmw-gh4p"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41159.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-41159","tags":["advisory"]},{"url":"https://github.com/mermaid-js/mermaid","tags":["package"]},{"url":"https://ubuntu.com/security/CVE-2026-41159","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-41159","tags":["report"]},{"url":"https://github.com/mermaid-js/mermaid/commit/64769738d5b59211e1decb471ffbaca8afec51aahttps://github.com/mermaid-js/mermaid/commit/a9d9f0d8eb790349121508688cd338253fd80d76","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-41159","title":"Mermaid: Improper sanitization of configuration leads to CSS injection","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 \u0026 (scope reference) handling. :not(\u0026) 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.","status":"published","published":"2026-05-29T13:53:10.148Z","modified":"2026-07-01T19:21:36.047Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium","assessor":"cna"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T13:41:19.694734Z"}],"euvd":[{"id":"EUVD-2026-33324","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 \u0026 (scope reference) handling. :not(\u0026) 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.","status":"published","published":"2026-05-29T13:53:10Z","modified":"2026-07-01T19:21:36Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium"}],"updated_at":"2026-11-02T18:20:18.588227Z"}],"ghsa":[{"id":"GHSA-87f9-hvmw-gh4p","title":"Mermaid: Improper sanitization of configuration leads to CSS injection","description":"### Impact\n\nMermaid's default configuration allows injecting CSS that applies outside of the Mermaid diagram via the `fontFamily`, `themeCSS`, and `altFontFamily` configuration options.\n\nLive demo: [mermaid.live](https://mermaid.live/edit#pako:eNpNjktLxDAUhf9KvFBR6JS-60QQfODKlUvJ5k6TtsEmKTHFGUP-u-mI6Nmdy3fOPR56wwVQSBIvtXSUeAaD0e4ZlZxPDChhcLxFfwiEauOuLq_9Afv30ZpVczpaITS5kGox1qF2gfSeBwYhJAnThAyz-ewntI68vG5-0z3Z7e7IA9OQwmglB-rsKlJQwircLPgNZeAmocTPAi4GXGfHgOkQYwvqN2PUbzJuGSegA84f0a0LRyeeJI4W_xChubCPcbQD2pwbgHo4Aq2aKmvbqq3zoiu7pizqFE6RybN9VFfFY1HWXRVS-Dr_zLObrt7_V_gGGXZlGg)\n\nExample code:\n\n```\n%%{init: {\"fontFamily\": \"x;a{b} :not(\u0026){background:green !important} c{d}\"}}%%\nflowchart LR\n    A --\u003e B\n```\n\nThe injected CSS exploits stylis's `\u0026` (scope reference) handling. `:not(\u0026)` 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.\n\nThis allows page defacement and DOM attribute exfiltration via CSS `:has()` selectors.\n\n### Patches\n\n- [v11.15.0](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0) (see [64769738d5b59211e1decb471ffbaca8afec51aa](https://github.com/mermaid-js/mermaid/commit/64769738d5b59211e1decb471ffbaca8afec51aa))\n- [v10.9.6](https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6) (see [a9d9f0d8eb790349121508688cd338253fd80d76](https://github.com/mermaid-js/mermaid/commit/a9d9f0d8eb790349121508688cd338253fd80d76))\n\n### Workarounds\n\nIf you can't upgrade mermaid, you can set the [`secure`](https://mermaid.js.org/config/schema-docs/config.html#secure) config value in the mermaid config to avoid allowing diagrams to modify `fontFamily`, `themeCSS`, `altFontFamily`, and `themeVariables`.\n\nSetting [`\"securityLevel\": \"sandbox\"`](https://mermaid.js.org/config/schema-docs/config.html#securitylevel)  will also prevent this.\n\n### Credits\n\nReported by @zsxsoft on behalf of @KeenSecurityLab","status":"published","published":"2026-05-11T19:37:00Z","modified":"2026-06-09T10:29:19Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T14:40:22.540562Z"}],"nvd":[{"id":"CVE-2026-41159","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 \u0026 (scope reference) handling. :not(\u0026) 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.","status":"published","published":"2026-05-29T15:16:22.813Z","modified":"2026-07-21T12:10:00.09Z","cvss":[{"version":"4.0","score":5.3,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"},{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"primary"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T14:12:21.244426Z"}],"osv":[{"id":"CVE-2026-41159","title":"Mermaid: Improper sanitization of configuration leads to CSS injection","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 \u0026 (scope reference) handling. :not(\u0026) 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.","status":"published","published":"2026-05-29T13:53:10.148Z","modified":"2026-10-28T02:30:32.62129895Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T15:45:03.424067Z"},{"id":"DEBIAN-CVE-2026-41159","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 \u0026 (scope reference) handling. :not(\u0026) 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.","status":"published","published":"2026-05-29T15:16:22.813Z","modified":"2026-10-01T03:03:11.632485124Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T15:45:54.892385Z"},{"id":"GHSA-87f9-hvmw-gh4p","title":"Mermaid: Improper sanitization of configuration leads to CSS injection","description":"### Impact\n\nMermaid's default configuration allows injecting CSS that applies outside of the Mermaid diagram via the `fontFamily`, `themeCSS`, and `altFontFamily` configuration options.\n\nLive demo: [mermaid.live](https://mermaid.live/edit#pako:eNpNjktLxDAUhf9KvFBR6JS-60QQfODKlUvJ5k6TtsEmKTHFGUP-u-mI6Nmdy3fOPR56wwVQSBIvtXSUeAaD0e4ZlZxPDChhcLxFfwiEauOuLq_9Afv30ZpVczpaITS5kGox1qF2gfSeBwYhJAnThAyz-ewntI68vG5-0z3Z7e7IA9OQwmglB-rsKlJQwircLPgNZeAmocTPAi4GXGfHgOkQYwvqN2PUbzJuGSegA84f0a0LRyeeJI4W_xChubCPcbQD2pwbgHo4Aq2aKmvbqq3zoiu7pizqFE6RybN9VFfFY1HWXRVS-Dr_zLObrt7_V_gGGXZlGg)\n\nExample code:\n\n```\n%%{init: {\"fontFamily\": \"x;a{b} :not(\u0026){background:green !important} c{d}\"}}%%\nflowchart LR\n    A --\u003e B\n```\n\nThe injected CSS exploits stylis's `\u0026` (scope reference) handling. `:not(\u0026)` 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.\n\nThis allows page defacement and DOM attribute exfiltration via CSS `:has()` selectors.\n\n### Patches\n\n- [v11.15.0](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.15.0) (see [64769738d5b59211e1decb471ffbaca8afec51aa](https://github.com/mermaid-js/mermaid/commit/64769738d5b59211e1decb471ffbaca8afec51aa))\n- [v10.9.6](https://github.com/mermaid-js/mermaid/releases/tag/v10.9.6) (see [a9d9f0d8eb790349121508688cd338253fd80d76](https://github.com/mermaid-js/mermaid/commit/a9d9f0d8eb790349121508688cd338253fd80d76))\n\n### Workarounds\n\nIf you can't upgrade mermaid, you can set the [`secure`](https://mermaid.js.org/config/schema-docs/config.html#secure) config value in the mermaid config to avoid allowing diagrams to modify `fontFamily`, `themeCSS`, `altFontFamily`, and `themeVariables`.\n\nSetting [`\"securityLevel\": \"sandbox\"`](https://mermaid.js.org/config/schema-docs/config.html#securitylevel)  will also prevent this.\n\n### Credits\n\nReported by @zsxsoft on behalf of @KeenSecurityLab","status":"published","published":"2026-05-11T19:37:00Z","modified":"2026-09-10T03:51:04.895749263Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T15:46:42.077781Z"},{"id":"UBUNTU-CVE-2026-41159","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 \u0026 (scope reference) handling. :not(\u0026) 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.","status":"published","published":"2026-05-29T15:16:00Z","modified":"2026-10-17T12:55:43.029302934Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium"},{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T16:56:16.686388Z"}]}}