# CVE-2026-30226: devalue has prototype pollution in devalue.parse and devalue.unflatten

> Attackers can cause denial of service or type confusion in Svelte devalue via prototype pollution in parse and unflatten functions.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Mar 2026
- **Updated:** 12 Mar 2026
- **Also known as:** GHSA-cfw5-2vxh-hr84, ROOT-APP-NPM-CVE-2026-30226

## What is CVE-2026-30226?

CVE-2026-30226 is a medium-severity vulnerability in sveltejs devalue, published on 11 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes)

## Which versions are affected by CVE-2026-30226?

2 open source packages ship an affected version, including devalue. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `devalue` | npm | All versions | 5.6.4 |
| `devalue` | npm | All versions | 5.6.4 |

Products: Svelte Devalue.

## How do I fix CVE-2026-30226?

Upgrade devalue to 5.6.4 or later.

## Is CVE-2026-30226 being exploited?

There is no known exploitation of CVE-2026-30226 in the wild and no public exploit code.

## Other vulnerabilities in sveltejs devalue

- [CVE-2026-42570](https://insights.sbomify.com/CVE-2026-42570/): Svelte devalue: DoS via sparse array deserialization (high 7.5)
- [CVE-2026-22774](https://insights.sbomify.com/CVE-2026-22774/): devalue vulnerable to denial of service due to memory exhaustion in devalue.parse (high 7.5)
- [CVE-2026-22775](https://insights.sbomify.com/CVE-2026-22775/): devalue vulnerable to denial of service due to memory/CPU exhaustion in devalue.parse (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-30226 and fix it if it is affected.

What it is: CVE-2026-30226 is a medium-severity vulnerability in sveltejs devalue, published on 11 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-30226 in the wild and no public exploit code.

Affected packages and fixed versions:
- devalue (npm): affected all versions; fixed in 5.6.4
- devalue (npm): affected all versions; fixed in 5.6.4

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-30226/ (Markdown: https://insights.sbomify.com/CVE-2026-30226/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-30226
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-30226
- OSV: https://osv.dev/vulnerability/CVE-2026-30226

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-30226/
Summaries are generated and may contain mistakes; the official description above is the record.