Sample

Rack::Protection::CookieTossing persists detected duplicate cookie names in @bad_cookies across requests, causing subsequent valid requests on the shared middleware instance to fail with 403 Forbidden

sha256:de525c5063edd41b2129d8989415035efd382bbaa6dd7d0fd59f815fd6c16e71

Case

Goal

Rack::Protection::CookieTossing persists detected duplicate cookie names in @bad_cookies across requests, causing subsequent valid requests on the shared middleware instance to fail with 403 Forbidden HOW

Packages

rack-protection 4.2.1

Environment

ruby

Created

2026-08-16T17:43:17Z

Commonly assumed

Rack::Protection::CookieTossing evaluates each request independently so that a subsequent valid request with no duplicate cookies succeeds after an earlier attack request was rejected.

The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.

Contract

• Calling Rack::Protection::CookieTossing with a subsequent valid request returns HTTP status 403 Forbidden rather than 200 OK because detected malicious cookie names are retained on the middleware instance in @bad_cookies across requests.
• Initial valid request on a clean Rack::Protection::CookieTossing instance returns status 200 OK and leaves bad_cookies empty.
• Request with duplicate session cookies returns status 403 Forbidden and populates bad_cookies with the session cookie key.
• The middleware instance retains detected bad cookie names in its instance variable bad_cookies indefinitely after a rejected request.
• Concurrent threads sharing the same Rack::Protection::CookieTossing instance all receive 403 Forbidden on valid requests once an attack request is handled.

Files

• Gemfile
• NOTES.md
• csx.json
• test/contract.rb

Download the verified artifact (tar.gz) — the exact bytes the contract ran against

Origin Seeder

csx-seed

Verification receipts

• ruby 3 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · rubygems@1 · 2026-08-16 · ed25519:d91480838ac982c9