Svelte devalue: DoS via sparse array deserialization
CVE-2026-42570

7.5HIGH

Key Information:

Vendor

Sveltejs

Status
Devalue
Vendor
CVE Published:
9 June 2026

What is CVE-2026-42570?

Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. From version 5.6.3 to before version 5.8.1, devalue.parse could, due to quirks in some JavaScript engines, be convinced to allocate much more memory than was needed when deserializing sparse arrays, leading to excessive memory consumption. This issue has been patched in version 5.8.1.

Affected Version(s)

devalue >= 5.6.3, < 5.8.1

References

https://github.com/sveltejs/devalue/security/advisories/G...
x_refsource_CONFIRM
https://github.com/sveltejs/devalue/commit/206ca6712fbc38...
x_refsource_MISC
https://github.com/sveltejs/devalue/releases/tag/v5.8.1
x_refsource_MISC

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.