CVE-2026-75931: high-severity vulnerability in fast-uri
fast-uri vulnerable to host confusion via skipped IDN canonicalization on scheme-relative references
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.4%
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Affected products
fast-uri · fast-uriRelated CVEs — fast-uri
In the same product, most dangerous first.
CVE-2026-13676HIGHfast-uri vulnerable to host confusion via failed IDN canonicalizationEPSS 0.7%CVE-2026-6321HIGHfast-uri vulnerable to path traversal via percent-encoded dot segmentsEPSS 0.6%CVE-2026-6322HIGHfast-uri vulnerable to host confusion via percent-encoded authority delimitersEPSS 0.5%CVE-2026-16221HIGHfast-uri vulnerable to host confusion via literal backslash authority delimiterEPSS 0.4%CVE-2026-84394HIGHfast-uri vulnerable to host confusion via an unclosed bracket in the URI authorityEPSS 0.4%CVE-2026-18446HIGHfast-uri vulnerable to host confusion via backslash authority introducerEPSS 0.4%