devalue: Malformed null-prototype object keys bypass __proto__ rejection via property-key coercion
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.
GHSA-4q55-j62x-fr9h
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:GHSA-4q55-j62x-fr9h
devalue
Source reference: /affected/0/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 5.9.3
Source reference:
/affected/0/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "SEMVER",
"events": [
{
"introduced": "0"
},
{
"fixed": "5.9.3"
}
]
}
],
"package": {
"name": "devalue",
"purl": "pkg:npm/devalue",
"ecosystem": "npm"
},
"database_specific": {
"source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-4q55-j62x-fr9h/GHSA-4q55-j62x-fr9h.json",
"last_known_affected_version_range": "<= 5.9.2"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #61118 · Revision 1
- Added to Heist Feed
- Publisher date