Improper Validation of Syntactic Correctness of Input Affecting rack package, versions >=3.0.0.beta1, <3.1.21>=3.2.0, <3.2.6
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Test your applications- Snyk IDSNYK-RUBY-RACK-15878234
- published3 Apr 2026
- disclosed2 Apr 2026
- creditth4s1s
Introduced: 2 Apr 2026
NewCVE-2026-34835 (opens in a new tab)How to fix?
Upgrade rack to version 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 Improper Validation of Syntactic Correctness of Input in the Rack::Request component. An attacker can bypass host allowlist checks by supplying specially crafted Host headers containing invalid characters, potentially leading to unauthorized access or manipulation of application behavior by exploiting improper validation during host header parsing.