style-dictionary up to 5.4.3 Expand API prototype pollution

Summaryinfo

A vulnerability identified as problematic has been detected in style-dictionary up to 5.4.3. Affected by this vulnerability is an unknown functionality of the component Expand API. The manipulation leads to prototype pollution. This vulnerability is traded as CVE-2026-54639. An attack has to be approached locally. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in style-dictionary up to 5.4.3 and classified as problematic. This issue affects some unknown functionality of the component Expand API. The manipulation with an unknown input leads to a prototype pollution vulnerability. Using CWE to declare the problem leads to CWE-1321. The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Style Dictionary, a build system for creating cross-platform styles, has a prototype pollution vulnerability starting in version 4.3.0 and prior to version 5.4.4. Impact users have: direct usage of `convertTokenData(tokens, { output: 'object' });`; indirect usage, via using Expand API; and/or indirect usage via SD's transform lifecycle. 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. A patch has been published in version `5.4.4`. The only known workaround is to sanitize token data first. Whether using DTCG format or old Style Dictionary format, check the token data object recursively for any object keys that include `__proto__`.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-54639 since 06/15/2026. The exploitation is known to be easy. An attack has to be approached locally. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1059 for this issue.

Upgrading to version 5.4.4 eliminates this vulnerability. Applying the patch 209085d9782cfc0783c4d983f3f1bb2c515954ec is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Name

• style-dictionary

Version

• 5.4.0
• 5.4.1
• 5.4.2
• 5.4.3

License

• open-source

Website

• Product: https://github.com/style-dictionary/style-dictionary/

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