How severe is CVE-2026-42570?

CVE-2026-42570 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-42570 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (30th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-42570?

CVE-2026-42570 affects Svelte Devalue. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-42570?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-42570 have an EU (EUVD) identifier?

Yes. CVE-2026-42570 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35500.

When was CVE-2026-42570 published?

CVE-2026-42570 was published on 2026-06-09 and last updated on 2026-06-30.

CVE-2026-42570

CVE-2026-42570 is a high-severity vulnerability in Svelte Devalue with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-770.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (30th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-35500
Weakness: CWE-770
Affected product: Svelte Devalue
Published: 2026-06-09
Last modified: 2026-06-30

Description

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.

Frequently asked questions

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.
How severe is CVE-2026-42570?: CVE-2026-42570 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-42570 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (30th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42570?: CVE-2026-42570 affects Svelte Devalue. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-42570?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-42570 have an EU (EUVD) identifier?: Yes. CVE-2026-42570 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-35500.
When was CVE-2026-42570 published?: CVE-2026-42570 was published on 2026-06-09 and last updated on 2026-06-30.

References

Affected products (1)

cpe:2.3:a:svelte:devalue:*:*:*:*:*:node.js:*:*

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