How severe is GHSA-4q55-j62x-fr9h?

No CVSS score has been assigned to GHSA-4q55-j62x-fr9h yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-4q55-j62x-fr9h?

GHSA-4q55-j62x-fr9h affects the following packages: devalue (npm). Ecosystems affected: npm.

How do I fix GHSA-4q55-j62x-fr9h?

Update devalue to 5.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4q55-j62x-fr9h is resolved across your whole dependency graph.

How do I detect GHSA-4q55-j62x-fr9h in my npm dependencies?

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

How do I mitigate GHSA-4q55-j62x-fr9h 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-4q55-j62x-fr9h actively exploited in the wild?

No public exploit code has been indexed for GHSA-4q55-j62x-fr9h 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.

When was GHSA-4q55-j62x-fr9h published, and has it been updated?

GHSA-4q55-j62x-fr9h was published on October 1, 2026 and was last updated on October 1, 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

devalue: Malformed null-prototype object keys bypass proto rejection via property-key coercionGHSA-4q55-j62x-fr9h

Fix: sveltejs/devalue@9ec5130

GHSA-4q55-j62x-fr9h is a security vulnerability in devalue. A fix is available for devalue — see the affected versions and patch details below.

Published

Oct 1, 2026

Updated

Oct 1, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 1, 2026 · OSV.dev, FIRST.org (EPSS)

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.

377other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

devaluenpm

11.0Mdownloads / week

Description

This is another instance of https://github.com/sveltejs/devalue/security/advisories/GHSA-mwv9-gp5h-frr4, where some payloads could cause parse to create objects with a __proto__ own property. This on its own is not enough to cause prototype pollution, and indeed this is actually how JSON.parse works, but we decided to be a little more defensive here and not allow the creation of objects with __proto__ own-properties. It is very unlikely for this to cause any issues.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`devalue`	all versions	5.9.3`npm install devalue@5.9.3`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for devalue, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update devalue to 5.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4q55-j62x-fr9h 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

This is another instance of https://github.com/sveltejs/devalue/security/advisories/GHSA-mwv9-gp5h-frr4, where some payloads could cause `parse` to create objects with a `__proto__` own property. This on its own is not enough to cause prototype pollution, and indeed this is actually how `JSON.parse` works, but we decided to be a little more defensive here and not allow the creation of objects with `__proto__` own-properties. It is very unlikely for this to cause any issues.

O3 Security · Impact-Aware SCA

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devalue: Malformed null-prototype object keys bypass __proto__ rejection via property-key coercionGHSA-4q55-j62x-fr9h