Vulnerability · Published Mar 11, 2026 · Assigned by GitHub_M

CVE-2026-30226devalue has prototype pollution in devalue.parse and devalue.unflatten

Medium 6.3

In plain English

A medium-severity prototype pollution in devalue from sveltejs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.3Medium

Exploit odds (30 days)0.5%top 59.1% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. In devalue v5.6.3 and earlier, devalue.parse and devalue.unflatten were susceptible to prototype pollution via maliciously crafted payloads. Successful exploitation could lead to Denial of Service (DoS) or type confusion. This vulnerability is fixed in 5.6.4.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	devalue	5.6.4	GHSA-cfw5-2vxh-hr84

Affected products (as reported)

Vendor	Product	Versions
sveltejs	devalue	< 5.6.4

Weakness: CWE-1321 · Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

References

https://github.com/sveltejs/devalue/security/advisories/GHSA-cfw5-2vxh-hr84 x_refsource_CONFIRM