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CVE-2026-8161 affects multiparty 4.2.3 and earlier. The multipart/form-data parser mishandles attacker-controlled field names that collide with inherited Object.prototype properties such as proto, constructor, or toString. When such a field name is processed, the implementation attempts to call .push() on the inherited prototype value instead of on an expected array, resulting in a TypeError. Because the exception is not caught, it propagates and terminates the Node.js process, causing a denial of service in applications that accept multipart uploads through multiparty.
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2 valid exploits after Mallory filtered fakes, detection scripts, and README-only repos.
Repository contains a Python proof-of-concept exploit plus a self-contained Dockerized mock lab demonstrating CVE-2026-8161 in pillarjs multiparty. The main exploit file is secdos.py, which uses requests to send a crafted multipart/form-data POST with a field named __proto__ to a user-supplied URL. This targets vulnerable multiparty object key handling in multipart parsing, causing a TypeError and process crash, resulting in denial of service. After sending one or more requests, the script performs a follow-up GET to determine whether the service is returning 5xx or refusing connections, and prints PASS/FAIL accordingly. Repository structure: README.md explains the vulnerability, impact, timeline, and demo usage. secdos-burp-req provides a raw HTTP request version of the crash payload. docker-compose.yml builds two environments: a vulnerable Node/Express app using multiparty 4.2.3 behind nginx on localhost:8080, and a patched app using multiparty 4.3.0 on localhost:8081. mocklab/app/backend.js exposes GET /, GET /health, and POST /api/submit; the latter parses multipart uploads with multiparty and is the vulnerable sink. mocklab/app/package.json and package-fix.json switch between vulnerable and patched dependency versions. mocklab/gateway/default.conf proxies traffic to vulnerable_server:3000 and serves a custom 50x page when the backend crashes. Exploit capability is limited to service disruption; there is no shell, command execution, persistence, or data theft functionality. The included frontend and nginx gateway are primarily for demonstration and visual confirmation of backend failure.
This repository is a standalone proof-of-concept for CVE-2026-8161 affecting multiparty <= 4.2.3. The main exploit is secdos.py, a Python script that crafts a multipart/form-data POST request whose field name is __proto__. In vulnerable multiparty versions, parser state is stored in plain JavaScript objects and attacker-controlled names are looked up through the prototype chain. Using __proto__ can therefore return an inherited object instead of an expected array, and subsequent push() operations trigger a TypeError inside asynchronous parsing, crashing the Node.js process. The exploit capability is denial of service only; there is no shell, code execution, or persistence payload. Repository structure: secdos.py is the active exploit driver; secdos-burp-req is a raw HTTP request equivalent for manual replay/testing; README.md explains the bug, usage, and expected behavior. The mocklab directory contains a reproducible lab environment: mocklab/app/backend.js is an Express application exposing /api/submit and parsing uploads with multiparty; package.json pins vulnerable multiparty 4.2.3 while package-fix.json pins patched 4.3.0; index.ejs and static assets provide a browser upload UI; gateway/default.conf and gateway/Dockerfile define an nginx reverse proxy that fronts the vulnerable service and serves a custom 50x page when the backend crashes; docker-compose.yml launches both a vulnerable target on localhost:8080 and a patched comparison target on localhost:8081. Exploit flow in secdos.py: it accepts a target URL and optional request count, sets a Host header derived from the URL, sends one or more crafted multipart POST requests, then performs a follow-up GET to determine whether the service now returns 5xx or refuses connections. A positive result is reported as 'Collision payload accepted. [PASS]'. Because the script both triggers the crash and verifies service failure, it is an operational DoS PoC rather than a pure detector. The included lab demonstrates the vulnerable behavior behind nginx, where backend failure is observable via a 502/custom error page, and contrasts it with a patched server that safely handles the same request.
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Cross-references every affected SKU, including bundled OEM variants.
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