{"id":"CVE-2026-50159","revision":null,"records":[{"revision":"0cadfe04d0be4381a09333c1ea2281c2","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-50159","aliases":[],"title":"Mermaid allows CSS injection applying to sibling elements of the diagram","description":"Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Prior to 10.9.8 and 11.16.1, Mermaid is vulnerable to CSS injection via sibling combinator selectors generated from diagram-supplied class or id names. An attacker who can supply diagram text can inject arbitrary CSS into the rendered page, potentially altering the appearance or behavior of unrelated page elements. This issue is fixed in versions 10.9.8 and 11.16.1.","state":0,"publishedAt":"2026-08-06T19:55:27.994+00:00","modifiedAt":"2026-08-07T17:18:23.685+00:00","affected":[{"ecosystem":"Vendor product","name":"mermaid","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"mermaid-js\",\n                    \"product\": \"mermaid\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 10.9.8\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \">= 11.0.0-alpha.1, < 11.16.1\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 4.0","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","score":5.3,"severity":"MEDIUM"}],"references":["https://github.com/mermaid-js/mermaid/security/advisories/GHSA-6x64-9x62-f2gx","https://github.com/mermaid-js/mermaid/pull/8022","https://github.com/mermaid-js/mermaid/commit/12d472c9ed43f94814b110da8d7a9ae6dd5266ed","https://github.com/mermaid-js/mermaid/commit/7e83f1533318b307764d961906a73377266f4c5e","https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.16.1","https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-50159","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-50159","identifiers":["CVE-2026-50159"]},"retained":false,"historicalAffected":[]},{"revision":"0cf453e13a59446ebb4f7ad1f6db1e35","observedAt":"2026-11-07T11:32:55.37+00:00","statement":{"source":"euvd","id":"EUVD-2026-54243","aliases":["CVE-2026-50159","GHSA-6x64-9x62-f2gx"],"title":"Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Prior to 10.9.8 and 11.16.1, Mermaid is vulnerable to CSS injection via sibling combinator selectors generated from diagram-supplied cla…","description":"Mermaid is a JavaScript tool that uses Markdown-inspired text to create and modify diagrams and charts. Prior to 10.9.8 and 11.16.1, Mermaid is vulnerable to CSS injection via sibling combinator selectors generated from diagram-supplied class or id names. An attacker who can supply diagram text can inject arbitrary CSS into the rendered page, potentially altering the appearance or behavior of unrelated page elements. This issue is fixed in versions 10.9.8 and 11.16.1.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 4.0","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","score":5.3,"severity":null}],"references":["https://github.com/mermaid-js/mermaid/security/advisories/GHSA-6x64-9x62-f2gx","https://github.com/mermaid-js/mermaid/pull/8022","https://github.com/mermaid-js/mermaid/commit/12d472c9ed43f94814b110da8d7a9ae6dd5266ed","https://github.com/mermaid-js/mermaid/commit/7e83f1533318b307764d961906a73377266f4c5e","https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.16.1","https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-54243","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Aug 6, 2026, 7:55:27 PM","dateUpdated":"Aug 7, 2026, 5:18:23 PM"},"relatedAdvisories":[],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. 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Prior to 10.9.8 and 11.16.1, Mermaid is vulnerable to CSS injection via sibling combinator selectors generated from diagram-supplied class or id names. An attacker who can supply diagram text can inject arbitrary CSS into the rendered page, potentially altering the appearance or behavior of unrelated page elements. This issue is fixed in versions 10.9.8 and 11.16.1.","state":0,"publishedAt":"2026-08-06T22:17:17.18+00:00","modifiedAt":"2026-10-24T16:10:00.153+00:00","affected":[],"metrics":[{"system":"CVSS 4.0 · security-advisories@github.com · Secondary","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","score":5.3,"severity":"MEDIUM"}],"references":["https://github.com/mermaid-js/mermaid/commit/12d472c9ed43f94814b110da8d7a9ae6dd5266ed","https://github.com/mermaid-js/mermaid/commit/7e83f1533318b307764d961906a73377266f4c5e","https://github.com/mermaid-js/mermaid/pull/8022","https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.16.1","https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8","https://github.com/mermaid-js/mermaid/security/advisories/GHSA-6x64-9x62-f2gx"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-50159","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Awaiting Analysis","weaknesses":["CWE-94"],"productCriteria":[],"sourceDates":{"published":"2026-08-06T22:17:17.180","lastModified":"2026-10-24T16:10:00.153"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-50159","identifiers":["CVE-2026-50159"]},"retained":false,"historicalAffected":[]},{"revision":"b6130ede22a14c56986362bb77dfe753","observedAt":"2026-10-24T13:17:17.793+00:00","statement":{"source":"osv","id":"GHSA-6x64-9x62-f2gx","aliases":["CVE-2026-50159"],"title":"Mermaid allows CSS injection applying to sibling elements of the diagram","description":"### Summary\n\nMermaid does not fully restrict CSS to the rendered SVG subtree. Although selectors are prefixed with `#mermaid-X`, sibling (`~` and `+`) combinators can still escape the Mermaid container and inject styles to DOM elements adjacent to the diagram `<svg>`.\n\n**Most users of mermaid would not be affected by this**, as mermaid adds its `<svg>` as an only child of it's parent element. However, you may be affected if you manually insert the `<svg>` (or other elements) into the DOM yourself.\n\n### Details\n\nMermaid namespaces CSS through with a middleware intended to scope all rules to the diagram's SVG element. CSS nesting expands `& ~ * { ... }` to `#svgId ~ *`, which selects all sibling elements following the SVG in the DOM, outside the diagram boundary.\n\n### Impact\n\nAn attacker able to supply diagram source to a page (e.g., user-generated content rendered by Mermaid) could inject CSS rules affecting sibling elements to the diagram `<svg>` on the host page. This can be used for UI redressing, hiding content, conditional CSS-based probing, or phishing-style visual manipulation.\n\nJavaScript execution is not possible via this vector.\n\n### Patches\n\nThis has been patched in https://github.com/mermaid-js/mermaid/commit/12d472c9ed43f94814b110da8d7a9ae6dd5266ed and released in [Mermaid v11.16.1](https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1).\n\nA backport has been made for the v10 branch in 7e83f1533318b307764d961906a73377266f4c5e and was released in [Mermaid v10.9.8](https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8)\n\n### Workarounds\n\nIf you are inserting the `<svg>` into the DOM yourself, you can wrap it in an element with no other children, e.g. `<div><svg>...</svg></div>` or `element.innerHTML = svg`. Alternatively, you can use `mermaid.run()` or `mermaid.initialize()`  which will do this for you. \n\nSetting [\"securityLevel\": \"sandbox\"](https://mermaid.js.org/config/schema-docs/config.html#securitylevel) will also prevent this, or setting 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\nTo test, you can try using a `themeCSS` with `& + * { /* my CSS here */}` and see if it's applied outside of your mermaid `<svg>`.\n\n```mermaid-example\n---\nconfig:\n  themeCSS: |-\n    & + * { background:red !important; width:100vw !important; height:100vh !important; position:fixed !important; inset:0 !important; }\n---\ninfo\n```\n\n### References\n\n- GHSA-87f9-hvmw-gh4p/CVE-2026-41159 (related vulnerability)\n- https://github.com/mermaid-js/mermaid/commit/12d472c9ed43f94814b110da8d7a9ae6dd5266ed\n- https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1\n- https://github.com/mermaid-js/mermaid/commit/7e83f1533318b307764d961906a73377266f4c5e\n- https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8","state":0,"publishedAt":"2026-08-06T19:55:31+00:00","modifiedAt":"2026-09-10T03:51:13.1668079+00:00","affected":[{"ecosystem":"npm","name":"mermaid","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"11.0.0-alpha.1"},{"kind":"fixed","version":"11.16.1"}]}],"versions":[],"rawVersionEvidence":null},{"ecosystem":"npm","name":"mermaid","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"10.9.8"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V4","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","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/mermaid-js/mermaid/security/advisories/GHSA-6x64-9x62-f2gx","https://github.com/mermaid-js/mermaid/pull/8022","https://github.com/mermaid-js/mermaid/commit/12d472c9ed43f94814b110da8d7a9ae6dd5266ed","https://github.com/mermaid-js/mermaid/commit/7e83f1533318b307764d961906a73377266f4c5e","https://github.com/mermaid-js/mermaid","https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.16.1","https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8"],"sourceUrl":"https://github.com/advisories/GHSA-6x64-9x62-f2gx","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-6x64-9x62-f2gx","identifiers":["GHSA-6x64-9x62-f2gx","CVE-2026-50159"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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