Vulnerability-Lookup

CVE-2026-50159 (GCVE-0-2026-50159)

Vulnerability from cvelistv5 – Published: 2026-08-06 19:55 – Updated: 2026-08-07 17:18

Title

Mermaid allows CSS injection applying to sibling elements of the diagram

Summary

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.

Severity

5.3 (Medium)


                        
                          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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-94 - Improper Control of Generation of Code ('Code Injection')

Assigner

GitHub_M

References

6 references

URL	Tags
https://github.com/mermaid-js/mermaid/security/ad…	x_refsource_CONFIRM
https://github.com/mermaid-js/mermaid/pull/8022	x_refsource_MISC
https://github.com/mermaid-js/mermaid/commit/12d4…	x_refsource_MISC
https://github.com/mermaid-js/mermaid/commit/7e83…	x_refsource_MISC
https://github.com/mermaid-js/mermaid/releases/ta…	x_refsource_MISC
https://github.com/mermaid-js/mermaid/releases/ta…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
mermaid-js	mermaid	Affected: < 10.9.8 Affected: >= 11.0.0-alpha.1, < 11.16.1

Show details on NVD website

JSON

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GHSA-6X64-9X62-F2GX

Vulnerability from github – Published: 2026-08-06 19:55 – Updated: 2026-08-06 19:55

Summary

Mermaid allows CSS injection applying to sibling elements of the diagram

Details

Summary

Mermaid 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>.

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.

Details

Mermaid 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.

Impact

An 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.

JavaScript execution is not possible via this vector.

Patches

This has been patched in https://github.com/mermaid-js/mermaid/commit/12d472c9ed43f94814b110da8d7a9ae6dd5266ed and released in Mermaid v11.16.1.

A backport has been made for the v10 branch in 7e83f1533318b307764d961906a73377266f4c5e and was released in Mermaid v10.9.8

Workarounds

If 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.

Setting "securityLevel": "sandbox" will also prevent this, or setting the secure config value in the mermaid config to avoid allowing diagrams to modify fontFamily, themeCSS, altFontFamily, and themeVariables.

To test, you can try using a themeCSS with & + * { /* my CSS here */} and see if it's applied outside of your mermaid <svg>.

---
config:
  themeCSS: |-
    & + * { background:red !important; width:100vw !important; height:100vh !important; position:fixed !important; inset:0 !important; }
---
info

References

GHSA-87f9-hvmw-gh4p/CVE-2026-41159 (related vulnerability)
https://github.com/mermaid-js/mermaid/commit/12d472c9ed43f94814b110da8d7a9ae6dd5266ed
https://github.com/mermaid-js/mermaid/releases/tag/mermaid%4011.16.1
https://github.com/mermaid-js/mermaid/commit/7e83f1533318b307764d961906a73377266f4c5e
https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8

Severity

5.3 (Medium)


                  
                    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

Show details on source website

JSON

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        "name": "mermaid"
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    "github_reviewed_at": "2026-08-06T19:55:31Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### 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 `\u003csvg\u003e`.\n\n**Most users of mermaid would not be affected by this**, as mermaid adds its `\u003csvg\u003e` as an only child of it\u0027s parent element. However, you may be affected if you manually insert the `\u003csvg\u003e` (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\u0027s SVG element. CSS nesting expands `\u0026 ~ * { ... }` 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 `\u003csvg\u003e` 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 `\u003csvg\u003e` into the DOM yourself, you can wrap it in an element with no other children, e.g. `\u003cdiv\u003e\u003csvg\u003e...\u003c/svg\u003e\u003c/div\u003e` 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 `\u0026 + * { /* my CSS here */}` and see if it\u0027s applied outside of your mermaid `\u003csvg\u003e`.\n\n```mermaid-example\n---\nconfig:\n  themeCSS: |-\n    \u0026 + * { 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",
  "id": "GHSA-6x64-9x62-f2gx",
  "modified": "2026-08-06T19:55:31Z",
  "published": "2026-08-06T19:55:31Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-6x64-9x62-f2gx"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/pull/8022"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/commit/12d472c9ed43f94814b110da8d7a9ae6dd5266ed"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/commit/7e83f1533318b307764d961906a73377266f4c5e"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/mermaid-js/mermaid"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.16.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Mermaid allows CSS injection applying to sibling elements of the diagram"
}

ubuntu-cve-2026-50159

Vulnerability from osv_ubuntu

Published

2026-08-07 00:00

Modified

2026-08-07 00:00

Summary

Details

Severity

5.3 (Medium)


                    
                      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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-50159	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-50159	REPORT
	https://github.com/mermaid-js/mermaid/security/ad…	REPORT
	https://github.com/mermaid-js/mermaid/commit/12d4…	REPORT
	https://github.com/mermaid-js/mermaid/commit/7e83…	REPORT
	https://github.com/mermaid-js/mermaid/pull/8022	REPORT
	https://github.com/mermaid-js/mermaid/releases/ta…	REPORT
	https://github.com/mermaid-js/mermaid/releases/ta…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "node-mermaid",
            "binary_version": "8.13.8+~cs10.4.16-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "node-mermaid",
        "purl": "pkg:deb/ubuntu/node-mermaid@8.13.8+~cs10.4.16-1?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "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"
      ]
    }
  ],
  "aliases": [],
  "details": "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.",
  "id": "UBUNTU-CVE-2026-50159",
  "modified": "2026-08-07T00:00:00Z",
  "published": "2026-08-07T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-50159"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-50159"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mermaid-js/mermaid/security/advisories/GHSA-6x64-9x62-f2gx"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mermaid-js/mermaid/commit/12d472c9ed43f94814b110da8d7a9ae6dd5266ed"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mermaid-js/mermaid/commit/7e83f1533318b307764d961906a73377266f4c5e"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mermaid-js/mermaid/pull/8022"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mermaid-js/mermaid/releases/tag/mermaid@11.16.1"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/mermaid-js/mermaid/releases/tag/v10.9.8"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "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",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-50159"
  ]
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-50159 (GCVE-0-2026-50159)

GHSA-6X64-9X62-F2GX

Summary

Details

Impact

Patches

Workarounds

References

ubuntu-cve-2026-50159

Vulnerability from osv_ubuntu

Tags

Sightings

Nomenclature