Description
Impact: fast-uri versions from 2.3.1 through 4.1.0 (including the 3.x line up to 3.1.3 and the 2.x line up to 2.4.2) do not treat a literal backslash character (U+005C) as an authority delimiter. Node's native WHATWG URL parser, used by fetch, undici, and Node's http and https clients, normalizes the backslash to a forward slash for special schemes such as http, https, ws, wss, ftp, and file. As a result, the two parsers extract different hosts from the same input string. Applications that use fast-uri to enforce host-based policy such as allowlists, denylists, loopback or SSRF filtering, redirect validation, or outbound proxy routing before passing the same URL into Node's URL or fetch consumers can be steered to an unintended destination, including cloud metadata endpoints, loopback, or internal hosts.
Patches: upgrade to fast-uri 4.1.1, 3.1.4, or 2.4.3.
Workarounds: none.
Patches: upgrade to fast-uri 4.1.1, 3.1.4, or 2.4.3.
Workarounds: none.
No analysis available yet.
Remediation
No remediation available yet.
Tracking
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Advisories
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References
History
Mon, 20 Jul 2026 14:30:00 +0000
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ssvc
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Sun, 19 Jul 2026 14:45:00 +0000
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| Description | Impact: fast-uri versions from 2.3.1 through 4.1.0 (including the 3.x line up to 3.1.3 and the 2.x line up to 2.4.2) do not treat a literal backslash character (U+005C) as an authority delimiter. Node's native WHATWG URL parser, used by fetch, undici, and Node's http and https clients, normalizes the backslash to a forward slash for special schemes such as http, https, ws, wss, ftp, and file. As a result, the two parsers extract different hosts from the same input string. Applications that use fast-uri to enforce host-based policy such as allowlists, denylists, loopback or SSRF filtering, redirect validation, or outbound proxy routing before passing the same URL into Node's URL or fetch consumers can be steered to an unintended destination, including cloud metadata endpoints, loopback, or internal hosts. Patches: upgrade to fast-uri 4.1.1, 3.1.4, or 2.4.3. Workarounds: none. | |
| Title | fast-uri vulnerable to host confusion via literal backslash authority delimiter | |
| Weaknesses | CWE-436 | |
| References |
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| Metrics |
cvssV3_1
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Subscriptions
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Status: PUBLISHED
Assigner: openjs
Published:
Updated: 2026-07-20T13:53:42.583Z
Reserved: 2026-07-18T11:37:36.004Z
Link: CVE-2026-16221
Updated: 2026-07-20T13:53:37.076Z
No data.
No data.
OpenCVE Enrichment
No data.
Weaknesses
-
CWE-436
Interpretation Conflict