Style Dictionary - Prototype Pollution in convertTokenData utility function

Exploitation

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

CVSS

8.8 · CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

EPSS

• CVE-2026-54639: 0.36% estimated exploitation activity in the next 30 days; percentile 29.46 (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.

Impact Prototype pollution. A malicious user can create a token array [{ key: '{proto.foo}', value: 'malicious' }], when processed by convertTokenData() utility function, it will pollute the Object.prototype globally where {}.foo will equal { key: '{proto.foo}', value: 'malicious' }. This has been confirmed with a test/reproduction. You are impacted when: - direct usage of convertTokenData(tokens, { output: 'object' }); - indirect usage, via using Expand API https://styledictionary.com/reference/config/#expand. If your expand config deems it necessary to run expand (this means, if NOT: 1) set to false, 2) all subprops set to false, or 3) undefined), then we sync the sd.tokens property with the sd.tokenMap property by converting tokenData map back to object. - indirect usage via SD's transform lifecycle. Once your tokens are transformed, we also have to sync the sd.tokens property with the sd.tokenMap property. Impact is high for this when style-dictionary is used as an integration in…

Published by the source

28 Jul 2026, 22:23 UTC

Last modified by the source

28 Jul 2026, 22:23 UTC

Source last checked

26 Oct 2026, 13:00 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-vj5c-m527-mpff

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# Patch Next advisory brief: CVE-2026-54639

Advisory: Style Dictionary - Prototype Pollution in convertTokenData utility function
IDs: CVE-2026-54639, GHSA-vj5c-m527-mpff
Record: https://patchnext.com/advisories/cve-2026-54639 (revision 1, source checked 26 Oct 2026, 13:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: style-dictionary 5.4.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm style-dictionary: affected >= 4.3.0, < 5.4.4; fixed in 5.4.4

## Suggested inspection (read-only)
- `npm ls style-dictionary --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 style-dictionary.
- 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://github.com/advisories/GHSA-vj5c-m527-mpff (GitHub-reviewed advisory GHSA-vj5c-m527-mpff lists affected ranges: npm style-dictionary >=4.3.0 <5.4.4)

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