# CVE-2026-30226: devalue DoS — Fixed in 5.6.4

📦 npm

Not in CISA KEV

# CVE-2026-30226 — devalue

CVE-2026-30226 is a CWE-1321 vulnerability in devalue. A fix is available for devalue — see the affected versions and patch details below.

devalue has prototype pollution in devalue.parse and devalue.unflatten

Also known as[GHSA-cfw5-2vxh-hr84](/vulnerability/GHSA-cfw5-2vxh-hr84)

Published

Mar 11, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### No confirmed exploitation observed yet

-   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-2026-30226.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.5%probability of exploitation in next 30 days

Lower Risk+0.06%

Lower risk than most CVEs41th percentile — riskier than 41% of all scored CVEsHighest risk

0.00%0.33%0.66%1.00%0.1%0.5%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## 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.

409other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

`devalue`npm

26.9Mdownloads / week

## Description

Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. In devalue v5.6.3 and earlier, devalue.parse and devalue.unflatten were susceptible to prototype pollution via maliciously crafted payloads. Successful exploitation could lead to Denial of Service (DoS) or type confusion. This vulnerability is fixed in 5.6.4.

## Affected Packages

1 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

📦npm

`devalue` 

all versions

5.6.4`npm install devalue@5.6.4`

## Affected Products

1 product · 1 configurations

Application

`devalue`svelte

< 5.6.4

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 5.6.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-30226 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
    

## Frequently Asked Questions

Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. In devalue v5.6.3 and earlier, devalue.parse and devalue.unflatten were susceptible to prototype pollution via maliciously crafted payloads. Successful exploitation could lead to Denial of Service (DoS) or type confusion. This vulnerability is fixed in 5.6.4.

O3 Security · Impact-Aware SCA

### Is CVE-2026-30226 in your dependencies?

Find it across npm, including transitive dependencies.

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