CVE-2026-84394

fast-uri accepts a host that contains an unbalanced or misplaced authority bracket without reporting an error. A host that starts with an opening bracket but does not end with a closing bracket is neither validated as an IP literal nor canonicalized as a domain name, so parse() returns it as the host with error undefined, while Node's URL and the HTTP clients built on it resolve the same string to a different host. An application that reads the parsed host to make a host decision, such as an SSRF denylist, a redirect allowlist, or proxy routing, and then passes the original URL to an HTTP client evaluates its policy against a string that is not the host the request reaches. The same host is carried through normalize, equal, and resolve. This affects fast-uri versions 2.4.5, 3.1.6, and 4.1.3, and is fixed in 2.4.6, 3.1.7, and 4.1.4, where parse() reports a malformed host for any host that contains a bracket but is not a valid IPv6 literal.

• CWE-436

• https://cna.openjsf.org/security-advisories.htmlVendor Advisory
• https://github.com/fastify/fast-uri/security/advisories/GHSA-58mr-gqgx-xq4gMitigation, Vendor Advisory

Published

Sep 3, 2026

Last Modified

Sep 4, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-84387A improper neutralization of special elements used in a comm…7.2
• CVE-2026-84389A url redirection to untrusted site ('open redirect') vulner…3.1
• CVE-2026-84390A inclusion of sensitive information in source code vulnerab…9.8
• CVE-2026-84391A use of uninitialized variable vulnerability in Fortinet Fo…6.5
• CVE-2026-84392A NULL Pointer Dereference vulnerability [CWE-476] vulnerabi…2.7
• CVE-2026-84393A improper validation of certificate with host mismatch vuln…8.1
• CVE-2026-84397Adobe Experience Manager is affected by a stored Cross-Site …5.4
• CVE-2026-84398CM2507 IP cameras accept an empty password for a privileged …7.5
• CVE-2026-84400CareCam CM2507 IP cameras contain an insufficiently protecte…3.1
• CVE-2026-84408QND contains an improper access control vulnerability in a n…8.7
• CVE-2026-8441The WP Review Slider Pro plugin for WordPress is vulnerable …7.5
• CVE-2026-8442The WP Review Slider Pro plugin for WordPress is vulnerable …8.1