CVE-2026-34835

A flaw was found in Rack. A remote attacker could exploit this by sending a specially crafted Host header containing characters not permitted in standard hostnames. This malformed header bypasses hostname validation in applications using Rack::Request, leading to host header poisoning. This can enable an attacker to manipulate links, redirects, or origin validation within affected applications.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.