---
id: CVE-2026-123565
title: Devalue before 5.9.3 Quadratic Expansion Denial of Service via uneval
summary: >-
  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 …
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-400
vendor: sveltejs
product: devalue
affected:
  - devalue < 5.9.3
published: '2026-11-08'
updated: '2026-11-08'
sourceUpdated: '2026-11-08T01:38:04.469Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-123565'
references:
  - url: >-
      https://github.com/sveltejs/devalue/security/advisories/GHSA-mcm9-63f2-9j32
    label: GitHub Security Advisory (GHSA-mcm9-63f2-9j32)
  - url: >-
      https://www.vulncheck.com/advisories/devalue-before-5.9.3-quadratic-expansion-denial-of-service-via-uneval
    label: >-
      VulnCheck Advisory: Devalue before 5.9.3 Quadratic Expansion Denial of
      Service via uneval
tags:
  - cve.org
ingestedAt: '2026-11-08T02:43:18.660Z'
---

## Overview

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.

## Affected

- `devalue < 5.9.3`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.