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VulnerabilityPublished Updated

CVE-2026-54639: Style Dictionary - Prototype Pollution

Affects style-dictionarySource GCVE Database

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Not known to be exploited · CVSS 8.8 High : upgrade to 5.4.4 soon.

Data as of 30 Oct 2026, 07:30 UTC

CVSS 3.1 base score
8.8High
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 5.4.4
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade style-dictionary to 5.4.4.

Affected software

ProductAffectedFixed in
Homebrewstyle-dictionarypkg:brew/style-dictionaryOther threatsAffected
  • >=5.0.0 <5.4.4
Fixed in
  • 5.4.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

### 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 a NodeJS server application. Impact is moderate for when style-dictionary is used as an integration in a Web application. Impact is low for most common cases where the user of style-dictionary also maintains the tokens, and access is limited via read/write access to the repository/workflows where it is used. ### Patches A patch has been published: version `5.4.4`. Any version within range `>=4.3.0 <5.4.4` contains this vulnerability, see commit hash 209085d for when the vulnerability was added. See PR with repro + fix https://github.com/style-dictionary/style-dictionary/pull/1702 ### Workarounds A workaround is to sanitize your token data first. Whether using DTCG format or old Style Dictionary format, you have to check the token data object recursively for any object keys that include `__proto__`. You can do this with the StyleDictionary instance too, just ensure that expand has to be set to false to prevent the second method of this vulnerability from happening. ```js const sd = new StyleDictionary({ expand: false }); if (sd.allTokens.some(tok => tok.key.includes('__proto__')) { throw new Error('Found malicious token key, attempting to do prototype pollution.') } ```

References

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