Vulnerability Description
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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Openjsf | Fast-Uri | 2.4.5 |
Related Weaknesses (CWE)
References
- https://cna.openjsf.org/security-advisories.htmlVendor Advisory
- https://github.com/fastify/fast-uri/security/advisories/GHSA-58mr-gqgx-xq4gMitigationVendor Advisory
FAQ
What is CVE-2026-84394?
CVE-2026-84394 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 nei...
How severe is CVE-2026-84394?
CVE-2026-84394 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-84394?
Check the references section above for vendor advisories and patch information. Affected products include: Openjsf Fast-Uri.