GHSA-MWV9-GP5H-FRR4
Vulnerability from github – Published: 2026-03-12 16:38 – Updated: 2026-06-26 20:30
VLAI
Summary
Sveltejs devalue's `devalue.parse` and `devalue.unflatten` emit objects with `__proto__` own properties
Details
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
Severity
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "devalue"
},
"ranges": [
{
"events": [
{
"introduced": "4.0.0"
},
{
"fixed": "5.6.4"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [],
"database_specific": {
"cwe_ids": [
"CWE-1321"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-12T16:38:15Z",
"nvd_published_at": null,
"severity": "LOW"
},
"details": "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:\n\n```ts\nconst result = devalue.parse(/* input creating an object with a __proto__ property */);\nconst target = {};\nObject.assign(target, result); // target\u0027s prototype is now polluted\n```",
"id": "GHSA-mwv9-gp5h-frr4",
"modified": "2026-06-26T20:30:20Z",
"published": "2026-03-12T16:38:15Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/sveltejs/devalue/security/advisories/GHSA-mwv9-gp5h-frr4"
},
{
"type": "WEB",
"url": "https://github.com/sveltejs/devalue/commit/87c1f3ce3759765a061cfe34843ecc4b0711ba8d"
},
{
"type": "PACKAGE",
"url": "https://github.com/sveltejs/devalue"
},
{
"type": "WEB",
"url": "https://github.com/sveltejs/devalue/releases/tag/v5.6.4"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U",
"type": "CVSS_V4"
}
],
"summary": "Sveltejs devalue\u0027s `devalue.parse` and `devalue.unflatten` emit objects with `__proto__` own properties"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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