# CVE-2026-42570: devalue — Fixed in 5.8.1 📦 📦 npm Not in CISA KEV HIGH severity # CVE-2026-42570 — devalue HIGH [Fix: sveltejs/devalue@206ca67](https://github.com/sveltejs/devalue/commit/206ca6712fbc380a4571c59de9ab04b91110792d) CVE-2026-42570 is a high-severity (CVSS 7.5) CWE-770 vulnerability in devalue. A fix is available for devalue — see the affected versions and patch details below. Svelte devalue: DoS via sparse array deserialization Also known as[GHSA-77vg-94rm-hx3p](/vulnerability/GHSA-77vg-94rm-hx3p) Published Jun 9, 2026 Updated Oct 28, 2026 Affected 1 pkg Patched 1 / 1 Exploits None indexed Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS) ## Exploitation Status ### No confirmed exploitation observed yet - CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks. - CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment. Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42570. ## EPSS Exploitation Probability [via FIRST.org ↗](https://www.first.org/epss/) 0.4%probability of exploitation in next 30 days Lower Risk0.00% Lower risk than most CVEs34th percentile — riskier than 34% of all scored CVEsHighest risk 0.00%0.41%0.81%1.22%0.4%0.4%Jul 26Oct 26Nov 26 Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/). ## How urgent is this, really ## Where this sits among everything scored ## Real-World Exposure 1 pkg affected How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched. 411other npm packages depend on this — each one inherits the vulnerability until it's patched upstream `devalue`npm 27.2Mdownloads / week ## 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. ## Affected Packages 1 total 1 fixed Ecosystem Package Vulnerable range Fix 📦npm `devalue` ≥ 5.6.3&&< 5.8.1 5.8.1`npm install devalue@5.8.1` ## Affected Products 1 product · 1 configurations Application `devalue`svelte ≥ 5.6.3 && < 5.8.1 range ## Detection & mitigation playbook Open-source dependency 1. ### Detect Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for devalue, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version. 2. ### Fix Update devalue to 5.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42570 is resolved across your whole dependency graph. 3. ### Workarounds Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade. ## Fixing This On Your OS If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project. Red HatImportant This vulnerability is rated as Important. The \`devalue\` JavaScript library is susceptible to excessive memory consumption. Deserializing specially crafted sparse arrays can lead to resource exhaustion and a denial of service, impacting the availability of affected systems. Workaround published by Red Hat > Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Source: [Red Hat security advisory for CVE-2026-42570](https://access.redhat.com/security/cve/cve-2026-42570) (CC BY 4.0) Product Fixed in Advisory Red Hat Enterprise Linux 10 `rh-podman-desktop-0:1.1.2-1.el10_2` [RHSA-2026:57590](https://access.redhat.com/errata/RHSA-2026:57590) Red Hat Trusted Artifact Signer 1.4 `rhtas/rekor-search-ui-rhel9:1783327185` [RHSA-2026:37272](https://access.redhat.com/errata/RHSA-2026:37272) ## Frequently Asked Questions 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. O3 Security · Impact-Aware SCA ### Is CVE-2026-42570 in your dependencies? Find it across npm, including transitive dependencies. 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