How severe is GHSA-mwv9-gp5h-frr4?

No CVSS score has been assigned to GHSA-mwv9-gp5h-frr4 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-mwv9-gp5h-frr4?

GHSA-mwv9-gp5h-frr4 affects the following packages: devalue (npm). Ecosystems affected: npm.

How do I fix GHSA-mwv9-gp5h-frr4?

Update devalue to 5.6.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mwv9-gp5h-frr4 is resolved across your whole dependency graph.

How do I detect GHSA-mwv9-gp5h-frr4 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for devalue. 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.

How do I mitigate GHSA-mwv9-gp5h-frr4 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.

How does O3 Security protect against GHSA-mwv9-gp5h-frr4?

O3 pinpoints whether GHSA-mwv9-gp5h-frr4 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-mwv9-gp5h-frr4 actively exploited in the wild?

No public exploit code has been indexed for GHSA-mwv9-gp5h-frr4 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-mwv9-gp5h-frr4 published, and has it been updated?

GHSA-mwv9-gp5h-frr4 was published on March 12, 2026 and was last updated on May 14, 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

GHSA-mwv9-gp5h-frr4

Sveltejs devalue's `devalue.parse` and `devalue.unflatten` emit objects with `__proto__` own properties

Published

Mar 12, 2026

Updated

May 14, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Blast Radius

1 pkg affected

Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.

devaluenpm

9.1Mdownloads / week

Description

In some circumstances, devalue.parse and devalue.unflatten could emit objects with __proto__ own properties. This in and of itself is not a security vulnerability (and is possible with, for example, JSON.parse as well), but it can result in prototype injection if downstream code handles it incorrectly:

const result = devalue.parse(/* input creating an object with a __proto__ property */);
const target = {};
Object.assign(target, result); // target's prototype is now polluted

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`devalue`	≥ 4.0.0&&< 5.6.4	5.6.4

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for devalue. 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 devalue to 5.6.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-mwv9-gp5h-frr4 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 GHSA-mwv9-gp5h-frr4 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 GHSA-mwv9-gp5h-frr4. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

In some circumstances, `devalue.parse` and `devalue.unflatten` could emit objects with `__proto__` own properties. This in and of itself is not a security vulnerability (and is possible with, for example, `JSON.parse` as well), but it can result in prototype injection if _downstream_ code handles it incorrectly: ```ts const result = devalue.parse(/* input creating an object with a __proto__ property */); const target = {}; Object.assign(target, result); // target's prototype is now polluted ```

O3 Security · Impact-Aware SCA

Is GHSA-mwv9-gp5h-frr4 in your dependencies?

O3 detects GHSA-mwv9-gp5h-frr4 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works