CVE-2026-18446

A flaw was found in fast-uri. This vulnerability arises because fast-uri incorrectly parses Uniform Resource Identifiers (URIs) when a backslash is used in place of a forward slash to introduce the authority component. This discrepancy with Node's native WHATWG URL parser can lead to host confusion. A remote attacker could exploit this to bypass security policies, such as allowlists or Server-Side Request Forgery (SSRF) filters, potentially redirecting applications to unintended hosts.

This is an Important host confusion vulnerability in fast-uri, which can affect Red Hat products that use the library for URI parsing and security policy enforcement. The discrepancy in how fast-uri handles backslash-based URI authority introducers compared to Node.js's native URL parser can lead to bypasses of host-based security policies, such as allowlists or Server-Side Request Forgery (SSRF) filtering, potentially redirecting applications to arbitrary external hosts.

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.