beautiful-mermaid contains an SVG attribute injection issue that can lead to cross-site scripting (XSS)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N · score source

EPSS

• CVE-2026-26226: 0.57% estimated exploitation activity in the next 30 days; percentile 47.40 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

beautiful-mermaid versions prior to 0.1.3 contain an SVG attribute injection issue that can lead to cross-site scripting (XSS) when rendering attacker-controlled Mermaid diagrams. User-controlled values from Mermaid style and classDef directives are interpolated into SVG attribute values without proper escaping, allowing crafted input to break out of an attribute context and inject arbitrary SVG elements/attributes into the rendered output. When the generated SVG is embedded in a web page, this can result in script execution in the context of the embedding origin.

Published by the source

13 Feb 2026, 18:31 UTC

Last modified by the source

13 Feb 2026, 21:41 UTC

Source last checked

26 Oct 2026, 12:42 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-cgmm-x5ww-q5cr

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-cgmm-x5ww-q5cr

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# Patch Next advisory brief: CVE-2026-26226

Advisory: beautiful-mermaid contains an SVG attribute injection issue that can lead to cross-site scripting (XSS)
IDs: CVE-2026-26226, GHSA-cgmm-x5ww-q5cr
Record: https://patchnext.com/advisories/cve-2026-26226 (revision 3, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: beautiful-mermaid 0.1.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm beautiful-mermaid: affected < 0.1.3; fixed in 0.1.3

## Suggested inspection (read-only)
- `npm ls beautiful-mermaid --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on beautiful-mermaid.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-cgmm-x5ww-q5cr (OSV record GHSA-cgmm-x5ww-q5cr lists affected ranges: npm beautiful-mermaid >=0 <0.1.3 (fixed))
- Verified: https://github.com/advisories/GHSA-cgmm-x5ww-q5cr (GitHub-reviewed advisory GHSA-cgmm-x5ww-q5cr lists affected ranges: npm beautiful-mermaid >=0 <0.1.3)

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