Sveltejs devalue's `devalue.parse` and `devalue.unflatten` emit objects with `__proto__` own properties
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 pollutedAffected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | devalue | >= 4.0.0, < 5.6.4 | 5.6.4 |
References
- CVSS vector
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- Weakness (CWE)
CWE-1321- Platform
- npm
- Package
devalue- Disclosed
- 12.03.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-mwv9-gp5h-frr4 - CC BY 4.0
Vulnerability history: devalue
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 16
- First → latest
- 08.2025 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 8
- Medium 4
- Low 4
Disclosures per year
- 2025: 1
- 2026: 15
-
Sveltejs devalue's `devalue.parse` and `devalue.unflatten` emit objects with `__proto__` own properties this entry
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