{"id":"GHSA-f65p-4m7j-42xc","summary":"fast-uri vulnerable to server-side request forgery via malformed IPv6 normalization","details":"### Impact\n\n`fast-uri` does not validate the complete RFC 3986 grammar for bracketed IPv6 literals, so a malformed literal with invalid trailing text is silently truncated to a different valid IPv6 address with no error reported. For example, `normalize('http://[::not-valid]/private')` returns `http://[::]/private`, and `[fc00::not-hex]` and `[fe80::not-hex]` collapse to `[fc00::]` and `[fe80::]`. An application that normalizes an untrusted URL before an outbound request, redirect, or host-policy check can be routed to a local or private address such as loopback (`::1`), unique-local, or link-local. Because `parse().error` is unset for these inputs, checking it does not protect the consumer.\n\n### Patches\n\nUpgrade to `fast-uri` 2.4.5, 3.1.6, or 4.1.3. Malformed IPv6 literals are now rejected with a host error instead of being normalized to a valid address.\n\n### Workarounds\n\nReject untrusted URLs whose host is a bracketed IPv6 literal before passing them to `fast-uri`, or route outbound requests against an explicit allowlist of addresses rather than trusting the normalized host.","aliases":["CVE-2026-75975"],"modified":"2026-09-02T16:00:14.091611548Z","published":"2026-09-02T15:43:30Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-09-02T15:43:30Z","nvd_published_at":"2026-08-24T10:16:40Z","cwe_ids":["CWE-20","CWE-918"],"severity":"HIGH"},"references":[{"type":"WEB","url":"https://github.com/fastify/fast-uri/security/advisories/GHSA-f65p-4m7j-42xc"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-75975"},{"type":"WEB","url":"https://github.com/fastify/fast-uri/commit/3728465caacef4b16bc84b7d14760f1c8fe41595"},{"type":"WEB","url":"https://github.com/fastify/fast-uri/commit/607bfbe953f28a14c2e06ae64aff38c81ca2937f"},{"type":"WEB","url":"https://github.com/fastify/fast-uri/commit/9161eded1ff55fad9d9714c6ad6c0f0283547799"},{"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/v2.4.5"},{"type":"WEB","url":"https://github.com/fastify/fast-uri/releases/tag/v3.1.6"},{"type":"WEB","url":"https://github.com/fastify/fast-uri/releases/tag/v4.1.3"}],"affected":[{"package":{"name":"fast-uri","ecosystem":"npm","purl":"pkg:npm/fast-uri"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.3.1"},{"fixed":"2.4.5"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-f65p-4m7j-42xc/GHSA-f65p-4m7j-42xc.json"}},{"package":{"name":"fast-uri","ecosystem":"npm","purl":"pkg:npm/fast-uri"},"ranges":[{"type":"SEMVER","events":[{"introduced":"3.0.0"},{"fixed":"3.1.6"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-f65p-4m7j-42xc/GHSA-f65p-4m7j-42xc.json"}},{"package":{"name":"fast-uri","ecosystem":"npm","purl":"pkg:npm/fast-uri"},"ranges":[{"type":"SEMVER","events":[{"introduced":"4.0.0"},{"fixed":"4.1.3"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-f65p-4m7j-42xc/GHSA-f65p-4m7j-42xc.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"}]}