---
id: "CVE-2026-123564"
page: "https://infrastack.ai/live/CVE-2026-123564"
kind: "vulnerability"
aliases: ["CVE-2026-123564"]
title: "devalue: sparse array serialization exhausts memory in browser or runtime"
severity: "high"
cvss: 8.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["browser", "javascript", "node.js", "package", "svelte", "sveltekit"]
not_affected_if: ["devalue-5.9.3-or-later", "no-uneval-use", "trusted-input-only"]
published_at: "2026-11-08T02:16:48+00:00"
first_seen_at: "2026-11-08T02:21:11+00:00"
updated_at: "2026-11-08T02:23:03+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123564", "first_seen_at": "2026-11-08T02:21:11+00:00"}]
exploit_sources: []
---

# devalue: sparse array serialization exhausts memory in browser or runtime

Link for people: https://infrastack.ai/live/CVE-2026-123564 (this .md is for agents)

devalue is a JavaScript library that serializes values, and its uneval output for sparse arrays allocates memory proportional to the declared array length when evaluated. An attacker who can influence a very large sparse array the application serializes can exhaust memory in the browser or runtime that evaluates the output.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed devalue version with `npm ls devalue` in the project.
- Search the lockfile for `devalue` and see whether any resolved version is below `5.9.3`.
- Look for uses of `uneval` in the application code and whether the output is evaluated.

## Fix

- devalue: move to `5.9.3` or later.

## Timeline

- 2026-11-08T02:21:11+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123564

## Documents

- [advisory] Vendor advisory: github.com https://github.com/sveltejs/devalue/security/advisories/GHSA-wf3x-273g-mvxv
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/sveltejs-devalue-before-5.9.3-memory-exhaustion-via-uneval-sparse-arrays

## From the sources

Sveltejs devalue from 1.0.0 before 5.9.3 contains a memory exhaustion flaw in uneval, whose generated code for sparse arrays allocates memory proportional to the array's declared length when evaluated. Attackers who can influence a very large sparse array serialized by an application can exhaust memory in the browser or runtime evaluating the output.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_