CVE-2026-8161
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · unedited[email protected] and lower versions are vulnerable to denial of service via uncaught exception. By sending a multipart/form-data request with a field name that collides with an inherited Object.prototype property such as __proto__, constructor, or toString, the parser invokes .push() on the inherited prototype value rather than an array, throwing a TypeError that propagates as an uncaught exception and crashes the process. Impact: any service accepting multipart uploads via multiparty is affected. Workarounds: none. Upgrade to [email protected] or higher.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe multiparty library versions 4.2.3 and below fail to validate field names in multipart/form-data requests against inherited Object.prototype properties. When a field name like __proto__, constructor, or toString is sent, the parser attempts to call .push() on the inherited prototype value instead of an array, causing a TypeError that crashes the Node.js process.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 4.3.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check multiparty version in useRun 'npm list multiparty' in your project directory or inspect node_modules/multiparty/package.json to find the installed versionAffected if The installed version is 4.2.3 or lower (any version below 4.3.0)
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Identify if your application uses multiparty for file uploadsSearch your codebase for 'require("multiparty")' or 'import multiparty' and verify the Form class is instantiated to handle multipart/form-data requestsAffected if Your application uses multiparty Form to parse incoming multipart requests
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Check if user-supplied field names reach the multipart parser without sanitizationInspect your code where form.parse() is called - look for whether field name parameters from the request are passed directly to the parser without filtering prototype property names like __proto__, constructor, or toStringAffected if User input field names are passed directly to form.parse() without filtering Object.prototype properties
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Look for crash logs or TypeError occurrencesSearch your application logs for 'TypeError' messages mentioning '.push is not a function' or similar errors occurring during multipart request processingAffected if Your application has crashed with a TypeError when processing multipart form data containing field names like __proto__
You are affected if multiparty version is below 4.3.0 AND your application parses multipart form data from untrusted sources without filtering field names for prototype properties.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped4.3.0
Upgrade multiparty to version 4.3.0 or higher, which includes proper prototype property filtering in the multipart field parser.
- Run `npm install [email protected]` to install the fixed version, or update your package.json dependency to "multiparty": ">=4.3.0" and run `npm install`
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation1.0 h
- Implementation1.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-8161 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-8161 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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