CVE-2026-84394fast-uri vulnerable to host confusion via an unclosed bracket in the URI authority
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- Weakness (CWE)
- CWE-436
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- openjs
- NVD analysis
- Analyzed
- Record last updated
- Sep 3, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
fast-uri fast-uri fast_uri:fast_uri (from the name) | from 2.4.5 before 2.4.6; 2.4.6 not affected; from 3.1.6 before 3.1.7; 3.1.7 not affected; from 4.1.3 before 4.1.4; 4.1.4 not affected | CNA record |
openjsf fast-uri openjsf:fast-uri | 2.4.5; 3.1.6; 4.1.3 | NVD |
References
- https://github.com/fastify/fast-uri/security/advisories/GHSA-58mr-gqgx-xq4gmitigation, vendor-advisory
- https://cna.openjsf.org/security-advisories.htmlvendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.