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CVE-2026-46510 kaspernj CVE debrief

form-data-objectizer prior to 1.0.1 is vulnerable to prototype pollution via bracket-notation form keys. An attacker can submit an HTTP form field with a name starting with `__proto__[...]` to mutate `Object.prototype`, affecting the entire Node.js process. This is a HIGH severity vulnerability (CVSS 8.2) with network attack vector, low complexity, and no privileges required. The issue is fixed in version 1.0.1.

Vendor
kaspernj
Product
form-data-objectizer
CVSS
HIGH 8.2
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-29
Original CVE updated
2026-07-21
Advisory published
2026-05-29
Advisory updated
2026-07-21

Who should care

Organizations using form-data-objectizer versions prior to 1.0.1 in Node.js applications that process untrusted form data. This includes web applications, API services, and any server-side code handling multipart/form-data or URL-encoded form submissions.

Technical summary

The form-data-objectizer library converts FormData to JavaScript objects. When processing bracket-notation keys (e.g., `name[sub]`), the library recursively builds nested objects without validating against dangerous property names. A form field named `__proto__[polluted]` causes assignment to `Object.prototype.polluted`, polluting the prototype chain for all objects in the Node.js process. This enables attackers to modify application behavior, potentially leading to denial of service or code execution depending on application logic.

Defensive priority

HIGH

Recommended defensive actions

  • Upgrade form-data-objectizer to version 1.0.1 or later
  • Validate and sanitize all incoming form field names before processing
  • Implement input filtering to reject keys containing `__proto__`, `constructor`, or `prototype`
  • Review application code for prototype pollution patterns if using affected versions
  • Monitor for suspicious form submissions with bracket-notation keys targeting prototype properties

Evidence notes

The vulnerability exists in form-data-objectizer versions prior to 1.0.1. The root cause is improper filtering of special property names (`__proto__`, `constructor`, `prototype`) when parsing bracket-notation form keys. The fix commit 7c54b99408e6e9cd6533b7245bf197dadc2a2dbc addresses this issue.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-46510 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-46510

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-46510 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-46510

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.