CVE-2026-75975
Description
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.
Statement
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.
Mitigation
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | High | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Integrity
Technical Impact: Execute Unauthorized Code or Commands
Access Control
Technical Impact: Bypass Protection Mechanism
By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
