CVE-2026-84394

A flaw was found in fast-uri. The library incorrectly processes Uniform Resource Identifier (URI) hosts containing unbalanced brackets, leading to a discrepancy in how the host is parsed by fast-uri compared to other HTTP clients. This host confusion can allow an attacker to bypass security policies, such as Server-Side Request Forgery (SSRF) denylists or redirect allowlists, by causing an application to evaluate its policy against an incorrect host string. This could result in unintended network requests or access to unauthorized resources.

This vulnerability is rated as an Important severity flaw because an unauthenticated remote attacker can exploit URI parsing discrepancies to bypass critical host-level access restrictions, such as SSRF filters or reverse proxy routing, without needing elevated privileges. Within Red Hat environments, the issue primarily impacts services that rely on fast-uri to validate external destinations before dispatching requests via Node.js HTTP clients. Product components that only provide frontend interfaces or do not evaluate host security policies using the parsed authority data are not exposed to security filter circumvention.

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.