csvjson CVE-2025-57318
Prototype Pollution in csvjson via toSchemaObject headers.
The problem
csvjson <= 5.1.0 (all published versions) is affected by
CVE-2025-57318 (CWE-1321 Prototype Pollution). The published package has
no fix available — exactly what npm audit reports. `csvjson.toSchemaObject()` interprets dotted/bracketed CSV column headers (e.g. `name.first`) to build nested objects. With no guard on reserved property names, a header such as `__proto__.polluted` or `constructor.prototype.polluted` causes the schema builder to walk into and mutate `Object.prototype`, affecting every object in the process (the `__proto__[]` variant instead throws, a denial-of-service). The attacker only needs to control the header row of a parsed CSV.
The fix — drop-in, no code changes
Add an overrides entry so every direct and transitive dependency on
csvjson resolves to the patched fork, then reinstall:
{
"overrides": {
"csvjson": "npm:@keep-lts/csvjson@^5.1.1"
}
}Equivalent for Yarn: use resolutions. The public API is unchanged — nothing else to do.
✓ Live on npm: @keep-lts/csvjson · or install directly: npm i @keep-lts/csvjson
This is rarely the only one
If csvjson turned up in your npm audit, there are very likely other abandoned dependencies in the same tree whose CVEs also have no fix on npm. Send us your npm audit output — or your Snyk / Dependabot list — and we'll tell you, for free, which of those findings we already fix. No call, no obligation.
Mid-audit and need a vendor on the hook? Keep LTS Pro adds an SLA on future CVEs and the SBOM / VEX artefacts your auditor will accept — all async, no calls.
What we changed
`addDataInSchema` now splits each header on `.`, `[`, and `]` and rejects the header if any segment is `__proto__`, `constructor`, or `prototype`. Legitimate nested headers — and headers that merely contain those words as substrings, e.g. `constructorName` — are unaffected.
Proof of concept (the vulnerability)
const csvjson = require('csvjson');
csvjson.toSchemaObject('__proto__.polluted\nyes');
console.log(({}).polluted); // => 'yes'@keep-lts/csvjson@5.1.1How we keep it trustworthy
- Minimal, surgical patch — security only, no feature changes.
- A regression test that fails on the original and passes on the patch; legitimate behaviour preserved.
- Published under the
@keep-ltsorg with the full advisory and tests inside the package; upstream license & attribution retained.
Full advisory and changelog ship inside the package (SECURITY.md, CHANGELOG.md).