CVE-2026-16221

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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://cna.openjsf.org/security-advisories.html
https://github.com/fastify/fast-uri/security/advisories/GHSA-v2hh-gcrm-f6hx

Configurations

No configuration.

History

19 Jul 2026, 15:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-07-19 15:16

Updated : 2026-07-21 18:31

NVD link : CVE-2026-16221

Mitre link : CVE-2026-16221

CVE.ORG link : CVE-2026-16221

JSON object : View

Products Affected

No product.

CWE

CWE-436

Interpretation Conflict

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