Description
fast-uri is a URI parser for Node.js. It canonicalizes a host to its ASCII form only when the input carries an explicit scheme, so a scheme-relative reference such as a host preceded by two slashes is returned with its host verbatim and no error set. As a result fast-uri's own entry points disagree with each other: parse, resolve, normalize, and equal can yield different hosts for the same input depending only on whether a scheme is written out, and equal can return opposite verdicts for the same pair of hosts. An application that extracts a host with fast-uri to check it against a policy list and then resolves the same reference can make its decision on one host while the destination is another, enabling host confusion and policy bypass. The affected versions are 2.4.2 up to but not including 2.4.5, 3.1.3 up to but not including 3.1.6, and 4.0.1 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which canonicalize the host consistently across the resolve path. Users should upgrade to a patched version.
Published: 2026-08-24
Score: 7.5 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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Remediation

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History

Thu, 27 Aug 2026 18:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-444
References
Metrics threat_severity

None

 threat_severity

Important

Tue, 25 Aug 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Mon, 24 Aug 2026 10:45:00 +0000

Type Values Removed Values Added
First Time appeared Fast-uri
Fast-uri fast-uri
Vendors & Products Fast-uri
Fast-uri fast-uri

Mon, 24 Aug 2026 09:45:00 +0000

Type Values Removed Values Added
Description fast-uri is a URI parser for Node.js. It canonicalizes a host to its ASCII form only when the input carries an explicit scheme, so a scheme-relative reference such as a host preceded by two slashes is returned with its host verbatim and no error set. As a result fast-uri's own entry points disagree with each other: parse, resolve, normalize, and equal can yield different hosts for the same input depending only on whether a scheme is written out, and equal can return opposite verdicts for the same pair of hosts. An application that extracts a host with fast-uri to check it against a policy list and then resolves the same reference can make its decision on one host while the destination is another, enabling host confusion and policy bypass. The affected versions are 2.4.2 up to but not including 2.4.5, 3.1.3 up to but not including 3.1.6, and 4.0.1 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which canonicalize the host consistently across the resolve path. Users should upgrade to a patched version.
Title fast-uri vulnerable to host confusion via skipped IDN canonicalization on scheme-relative references
Weaknesses CWE-436
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}

Subscriptions

Fast-uri Fast-uri
cve-icon MITRE

Status: PUBLISHED

Assigner: openjs

Published:

Updated: 2026-08-24T16:28:48.098Z

Reserved: 2026-08-18T15:43:33.460Z

Link: CVE-2026-75931

cve-icon Vulnrichment

Updated: 2026-08-24T16:28:41.325Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-08-24T10:16:40.113

Modified: 2026-08-28T19:46:29.323

Link: CVE-2026-75931

cve-icon Redhat

Severity : Important

Publid Date: 2026-08-24T09:30:04Z

Links: CVE-2026-75931 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-08-28T19:45:03Z

Weaknesses