Interpretation Conflict Affecting rack package, versions <2.2.23>=3.0.0.beta1, <3.1.21>=3.2.0, <3.2.6
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Test your applications- Snyk IDSNYK-RUBY-RACK-15878035
- published3 Apr 2026
- disclosed2 Apr 2026
- creditAndrew Lacambra
Introduced: 2 Apr 2026
NewCVE-2026-26961 (opens in a new tab)How to fix?
Upgrade rack to version 2.2.23, 3.1.21, 3.2.6 or higher.
Overview
rack is a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.
Affected versions of this package are vulnerable to Interpretation Conflict in the Rack::Multipart::Parser component. An attacker can cause the application to interpret multipart form data differently from upstream proxies or WAFs by sending requests with multiple boundary parameters in the Content-Type header. This can allow malicious form fields or file uploads to bypass upstream inspection and be processed by the application.
Note:
This is only exploitable if an upstream proxy, WAF, or intermediary interprets the first boundary parameter while the application parses the last one.