GHSA-58mr-gqgx-xq4g
fast-uri vulnerable to host confusion via an unclosed bracket in the URI authority
Packages
Details
As written in the advisory (Markdown source, shown as plain text).
### Impact
`fast-uri` accepts a host that contains an unbalanced or misplaced authority bracket (`[` or `]`) without reporting an error. A host that starts with `[` but does not end with `]`, such as `[@127.0.0.1`, 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 `http.get`, `axios`, `got`, and other clients built on it) resolve the same string to `127.0.0.1`. An application that reads `parse().host` to make a host decision (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()`.
### Patches
This vulnerability has been patched in fast-uri `4.1.4`, `3.1.7`, and `2.4.6`. `parse()` now reports `URI host is malformed.` for any host that contains a bracket but is not a valid `[IPv6]` literal. All users should upgrade.
### Workarounds
If upgrading is not immediately possible, reject any URL whose host contains a `[` or `]` that is not a well-formed IPv6 literal before making a host decision. Clients that fail closed on credential-bearing URLs, such as Node's global `fetch()`, are not affected by the reported vector.
References
External links from the advisory. They lead to third-party sites.
- https://github.com/fastify/fast-uri/security/advisories/GHSA-58mr-gqgx-xq4g
- https://nvd.nist.gov/vuln/detail/CVE-2026-84394
- https://github.com/fastify/fast-uri/pull/214
- https://github.com/fastify/fast-uri/commit/e00815236bc94107e44ef1b2f5318a06bac225c0
- https://cna.openjsf.org/security-advisories.html
- https://github.com/fastify/fast-uri
- https://github.com/fastify/fast-uri/releases/tag/v2.4.6
- https://github.com/fastify/fast-uri/releases/tag/v3.1.7
- https://github.com/fastify/fast-uri/releases/tag/v4.1.4