GHSA-WJR9-J795-JXCR
Vulnerability from github – Published: 2026-10-23 21:37 – Updated: 2026-10-23 21:37Impact
fast-uri versions >= 2.4.2, <= 2.4.7, >= 3.1.3, <= 3.1.8, and >= 4.0.1, <= 4.2.2 can silently rewrite the host of an HTTP-family URL (http, https, ws, wss, or any scheme with domainHost: true). For those schemes canonicalizeHost() passes the parsed host to the WHATWG URL parser and adopts its .hostname without checking that the parser read the whole input as a host. RFC 3986 permits @ inside the host group and the WHATWG parser strips TAB, LF, and CR, so the authority fast-uri reports is rewritten by that second parser with no error set: data before an @ is dropped and whitespace is removed.
For example, fast-uri parses http://a@b@evil.example/ to host evil.example (dropping the b segment), and a host containing a raw TAB, CR, or LF has those characters stripped. equal() then treats a whitespace-smuggled host as the same as the clean one, and resolve() rewrites the authority the same way.
Applications that use fast-uri to enforce host-based policy (denylists, loopback filtering, redirect validation, outbound proxy routing) on one representation, such as the raw input, see a policy/use desync: the canonical host fast-uri returns differs from what was checked, and traffic can be steered to an unintended destination.
Patches
Upgrade to fast-uri 2.4.8, 3.1.9, or 4.2.3.
Workarounds
Reject URIs whose authority contains more than one @, or contains TAB, CR, or LF, before calling fast-uri. Alternatively, treat any non-empty parse(x).error as fatal, and compare hosts only from the same parse() result.
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "fast-uri"
},
"ranges": [
{
"events": [
{
"introduced": "2.4.2"
},
{
"fixed": "2.4.8"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "fast-uri"
},
"ranges": [
{
"events": [
{
"introduced": "3.1.3"
},
{
"fixed": "3.1.9"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "fast-uri"
},
"ranges": [
{
"events": [
{
"introduced": "4.0.1"
},
{
"fixed": "4.2.3"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-110180"
],
"database_specific": {
"cwe_ids": [
"CWE-20",
"CWE-436"
],
"github_reviewed": true,
"github_reviewed_at": "2026-10-23T21:37:59Z",
"nvd_published_at": "2026-10-20T07:17:08Z",
"severity": "MODERATE"
},
"details": "### Impact\n\n`fast-uri` versions `\u003e= 2.4.2, \u003c= 2.4.7`, `\u003e= 3.1.3, \u003c= 3.1.8`, and `\u003e= 4.0.1, \u003c= 4.2.2` can silently rewrite the host of an HTTP-family URL (`http`, `https`, `ws`, `wss`, or any scheme with `domainHost: true`). For those schemes `canonicalizeHost()` passes the parsed host to the WHATWG `URL` parser and adopts its `.hostname` without checking that the parser read the whole input as a host. RFC 3986 permits `@` inside the host group and the WHATWG parser strips TAB, LF, and CR, so the authority `fast-uri` reports is rewritten by that second parser with no `error` set: data before an `@` is dropped and whitespace is removed.\n\nFor example, `fast-uri` parses `http://a@b@evil.example/` to host `evil.example` (dropping the `b` segment), and a host containing a raw TAB, CR, or LF has those characters stripped. `equal()` then treats a whitespace-smuggled host as the same as the clean one, and `resolve()` rewrites the authority the same way.\n\nApplications that use `fast-uri` to enforce host-based policy (denylists, loopback filtering, redirect validation, outbound proxy routing) on one representation, such as the raw input, see a policy/use desync: the canonical host `fast-uri` returns differs from what was checked, and traffic can be steered to an unintended destination.\n\n### Patches\n\nUpgrade to `fast-uri` `2.4.8`, `3.1.9`, or `4.2.3`.\n\n### Workarounds\n\nReject URIs whose authority contains more than one `@`, or contains TAB, CR, or LF, before calling `fast-uri`. Alternatively, treat any non-empty `parse(x).error` as fatal, and compare hosts only from the same `parse()` result.",
"id": "GHSA-wjr9-j795-jxcr",
"modified": "2026-10-23T21:37:59Z",
"published": "2026-10-23T21:37:59Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/fastify/fast-uri/security/advisories/GHSA-wjr9-j795-jxcr"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-110180"
},
{
"type": "WEB",
"url": "https://github.com/fastify/fast-uri/commit/58c183d0b168ad87f98773266444ce1f6375803a"
},
{
"type": "WEB",
"url": "https://github.com/fastify/fast-uri/commit/ddfc6a51122dfce0365655f04479fc3adb7f6b3c"
},
{
"type": "WEB",
"url": "https://github.com/fastify/fast-uri/commit/f6d46dfeab025d0c440485f4ae29fa4f14707646"
},
{
"type": "WEB",
"url": "https://cna.openjsf.org/security-advisories.html"
},
{
"type": "PACKAGE",
"url": "https://github.com/fastify/fast-uri"
},
{
"type": "WEB",
"url": "https://github.com/fastify/fast-uri/releases/tag/v2.4.8"
},
{
"type": "WEB",
"url": "https://github.com/fastify/fast-uri/releases/tag/v3.1.9"
},
{
"type": "WEB",
"url": "https://github.com/fastify/fast-uri/releases/tag/v4.2.3"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "fast-uri vulnerable to host confusion via unchecked WHATWG host canonicalization"
}
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