CVE-2026-75975

A flaw was found in fast-uri, a URI parser for Node.js. Its custom parser for bracketed IPv6 literals does not fully validate the IPv6 grammar, allowing invalid trailing text in an authority to be silently discarded. This can lead to a malformed, attacker-controlled host being normalized into a different, valid IPv6 destination, such as a local or private IPv6 target. An application normalizing untrusted URLs before outbound requests, redirects, or proxy routing could be redirected, resulting in a server-side request forgery (SSRF) and address-policy bypass.

A Server-Side Request Forgery (SSRF) flaw was found in fast-uri, a URI parser for Node.js. The parser's incomplete validation of bracketed IPv6 literals allows attackers to inject malformed authority components that are silently normalized to different valid IPv6 destinations. This could allow an attacker to bypass URL allowlists or network-based access controls, potentially enabling unauthorized access to internal services, cloud metadata endpoints, or other network resources. This issue affects Red Hat products that bundle fast-uri as part of their Node.js dependencies. Fixed versions are available: fast-uri 2.4.5, 3.1.6, and 4.1.3.

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. Until updates are available, restrict the processing of user-supplied URIs to trusted sources only, implement strict allowlists for destination hosts (preferably IP-based rather than hostname-based), and apply egress filtering to prevent server-initiated connections to internal networks or cloud metadata services.