CVE-2026-42570: Svelte devalue Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-77vg-94rm-hx3p
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CVSS 7.5
CWE-770
Published
Advisory Summary

CVE-2026-42570 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting Svelte devalue libraries in the npm ecosystem. The issue involves dos via sparse array deserialization. Remediation is available by upgrading affected packages to version 5.8.1.

CVE-2026-42570 at a Glance

CVE Identifier CVE-2026-42570
GHSA Identifier GHSA-77vg-94rm-hx3p
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product Svelte devalue
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-42570

To remediate this vulnerability, upgrade all affected Svelte devalue dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

devalue fixed: 5.8.1 
npm install devalue@5.8.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls devalue

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-42570, inspect your project dependencies using npm:

npm ls devalue

Analyze the terminal output to locate any version of Svelte devalue in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.8.1), your application is affected.

Note: The npm ls devalue command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. In Svelte devalue, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

`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.

CVE-2026-42570 Affected Svelte devalue Versions

1 component(s)
Fixed Versions:
5.8.1
Product / Package Ecosystem Affected Versions Fixed Version
devalue
npm/devalue
npm
≥ 5.6.3
< 5.8.1
5.8.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/sveltejs/devalue/security/advisories/GHSA-77vg-94rm-hx3p
NVD — CVE-2026-42570 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-42570
Security Fix Commit FIX COMMIT
https://github.com/sveltejs/devalue/commit/206ca6712fbc380a4571c59de9ab04b91110792d
Svelte devalue Source Repository REPOSITORY
https://github.com/sveltejs/devalue
Svelte devalue Release RELEASE
https://github.com/sveltejs/devalue/releases/tag/v5.8.1

Frequently Asked Questions

What is CVE-2026-42570?
CVE-2026-42570 is a security vulnerability in Svelte devalue involving DoS via sparse array deserialization under CWE-770: Allocation of Resources Without Limits or Throttling.
Which Svelte devalue versions are affected?
Affected versions include releases prior to 5.8.1 across affected packages: devalue.
What version fixes CVE-2026-42570?
Upgrading to 5.8.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is devalue affected?
Yes, devalue is affected in releases prior to 5.8.1. Upgrade your dependency to 5.8.1 or later.
What is the CVSS score of CVE-2026-42570?
CVE-2026-42570 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-42570?
CVE-2026-42570 is classified under CWE-770: Allocation of Resources Without Limits or Throttling (The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.).
How can I check npm dependencies for CVE-2026-42570?
Run the dependency tree command: 'npm ls devalue'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-77vg-94rm-hx3p",
  "modified" : "2026-06-09T18:41:24Z",
  "published" : "2026-05-14T20:23:47Z",
  "aliases" : [ "CVE-2026-42570" ],
  "summary" : "Svelte devalue: DoS via sparse array deserialization",
  "details" : "`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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "devalue"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.6.3"
      }, {
        "fixed" : "5.8.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.8.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/devalue/security/advisories/GHSA-77vg-94rm-hx3p"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-42570"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/devalue/commit/206ca6712fbc380a4571c59de9ab04b91110792d"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sveltejs/devalue"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/devalue/releases/tag/v5.8.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-14T20:23:47Z",
    "nvd_published_at" : "2026-06-09T17:17:07Z"
  }
}