CVE-2026-54639 is a high-severity (CVSS 8.8) CWE-1321 vulnerability in style-dictionary. O3 Security confirms whether CVE-2026-54639 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Style Dictionary - Prototype Pollution in convertTokenData utility function
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
style-dictionarynpmDescription
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__.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | style-dictionary | ≥ 4.3.0&&< 5.4.4 | 5.4.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for style-dictionary. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update style-dictionary to 5.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54639 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-54639 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-54639. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-54639 in your dependencies?
O3 detects CVE-2026-54639 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.