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Vulnerability details

7.5/10
CVSS 3.1
GHSA-v2hh-gcrm-f6hx
resolved Published 2026-07-21 Updated 2026-07-21
GitHub Advisory
Vulnerability Data from Dependency-Track
Affected versions
Score
7.5 CVSS 3.1 GITHUB CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Description
### Impact `fast-uri` v4.1.0 and earlier do not treat a literal backslash (U+005C) as an authority delimiter. Node's native WHATWG `URL` (used by `fetch()`, `undici`, and Node's `http`/`https` clients) normalizes `\` to `/` for special schemes (`http`, `https`, `ws`, `wss`, `ftp`, `file`), so the two parsers extract different hosts from the same input string. For example, `http://evil.com\@allowed.com` is treated by `fast-uri` as host `allowed.com` with userinfo `evil.com\`, while Node's WHATWG URL parser and `fetch()` see host `evil.com` with path `/@allowed.com`. Applications that use `fast-uri` to enforce host-based policy (allowlists, denylists, loopback/SSRF filtering, redirect validation, outbound proxy routing) before passing the same URL into Node's URL or `fetch()` consumers see a policy/use desync and can be steered to an unintended destination, including cloud metadata endpoints, loopback, or internal hosts. ### Patches Upgrade to `fast-uri` v4.1.1, v3.1.4, or v2.4.3. ### Workarounds None. Upgrade to the patched version.
Same vulnerability as
CVE-2026-16221 resolved according to EUVD-2026-45551
Analysis Read only
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