CVE-2026-42570

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.

CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0038

Probability of exploitation

0.30%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-770 CWE-770

Affected Products

Vendor	Product	Versions
svelte	devalue	5.6.3 — 5.8.1

References

Advisories & Patches

https://github.com/sveltejs/devalue/commit/206ca6712fbc380a4571c59de9ab04b91110792d https://github.com/sveltejs/devalue/security/advisories/GHSA-77vg-94rm-hx3p

Other References

https://github.com/sveltejs/devalue/releases/tag/v5.8.1

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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-42570? +

CVE-2026-42570 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0038, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-42570? +

CVE-2026-42570 affects products from svelte, specifically: devalue. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-42570? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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