How severe is GHSA-vj5c-m527-mpff?

GHSA-vj5c-m527-mpff has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-vj5c-m527-mpff?

GHSA-vj5c-m527-mpff affects the following packages: style-dictionary (npm). Ecosystems affected: npm.

How do I fix GHSA-vj5c-m527-mpff?

Update style-dictionary to 5.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vj5c-m527-mpff is resolved across your whole dependency graph.

How do I detect GHSA-vj5c-m527-mpff in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for style-dictionary, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-vj5c-m527-mpff if there is no patch (or I can't update yet)?

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.

Is GHSA-vj5c-m527-mpff actively exploited in the wild?

No public exploit code has been indexed for GHSA-vj5c-m527-mpff yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-vj5c-m527-mpff?

GHSA-vj5c-m527-mpff has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 27th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-vj5c-m527-mpff?

GHSA-vj5c-m527-mpff is classified as CWE-1321 (CWE-1321). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-vj5c-m527-mpff published, and has it been updated?

GHSA-vj5c-m527-mpff was published on July 28, 2026 and was last updated on July 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

HIGH severity

GHSA-vj5c-m527-mpff — style-dictionary

HIGHFix: style-dictionary/style-dictionary#1702

GHSA-vj5c-m527-mpff is a high-severity (CVSS 8.8) CWE-1321 vulnerability in style-dictionary. A fix is available for style-dictionary — see the affected versions and patch details below.

Style Dictionary - Prototype Pollution in convertTokenData utility function

Also known asCVE-2026-54639

Published

Jul 28, 2026

Updated

Jul 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 26, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-vj5c-m527-mpff.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs27th percentile — riskier than 27% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-vj5c-m527-mpff by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

400other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

style-dictionarynpm

2.5Mdownloads / week

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.

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.')
}

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`style-dictionary`	≥ 4.3.0&&< 5.4.4	5.4.4`npm install style-dictionary@5.4.4`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for style-dictionary, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update style-dictionary to 5.4.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vj5c-m527-mpff 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.

Frequently Asked Questions

### 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 (thi