---
id: "CVE-2026-123565"
page: "https://infrastack.ai/live/CVE-2026-123565"
kind: "vulnerability"
aliases: ["CVE-2026-123565"]
title: "devalue: crafted payload exhausts memory and CPU through quadratic expansion"
severity: "high"
cvss: 8.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["javascript", "node", "package", "self-hosted", "svelte", "sveltekit"]
not_affected_if: ["devalue-not-used", "no-untrusted-input"]
published_at: "2026-11-08T02:16:49+00:00"
first_seen_at: "2026-11-08T02:21:12+00:00"
updated_at: "2026-11-08T02:23:03+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123565", "first_seen_at": "2026-11-08T02:21:12+00:00"}]
exploit_sources: []
---

# devalue: crafted payload exhausts memory and CPU through quadratic expansion

Link for people: https://infrastack.ai/live/CVE-2026-123565 (this .md is for agents)

devalue, a JavaScript library for serializing data, expands repeated primitive strings quadratically in its uneval function. A small crafted payload can produce a very large serialized string that exhausts memory or CPU.

_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 each project.
- Look for devalue in the dependency tree of any service that passes untrusted input to uneval.

## Fix

- devalue `5.9.3` or later (per the advisory title, versions before 5.9.3 are affected).

## Timeline

- 2026-11-08T02:21:12+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123565

## Documents

- [advisory] Vendor advisory: github.com https://github.com/sveltejs/devalue/security/advisories/GHSA-mcm9-63f2-9j32
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/devalue-before-5.9.3-quadratic-expansion-denial-of-service-via-uneval

## From the sources

Sveltejs devalue before 5.9.3 contains a resource exhaustion vulnerability where repeated primitive strings cause quadratic expansion in the uneval function. Attackers can supply a small crafted payload that is parsed and then passed to uneval, producing a very large serialized string that exhausts memory or CPU.

---

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