CVE-2026-75931fast-uri vulnerable to host confusion via skipped IDN canonicalization on scheme-relative references
Updated under an hour ago ()
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No exploitation reported and no EPSS estimate yet.
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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
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- Weakness (CWE)
- CWE-436
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- openjs
- NVD analysis
- Analyzed
- Record last updated
- Aug 24, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
fast-uri fast-uri fast_uri:fast_uri (from the name) | from 2.4.2 before 2.4.5; 2.4.5 not affected; from 3.1.3 before 3.1.6; 3.1.6 not affected; from 4.0.1 before 4.1.3; 4.1.3 not affected | CNA record |
openjsf fast-uri openjsf:fast-uri | from 2.4.2 before 2.4.5; from 3.1.3 before 3.1.6; from 4.0.1 before 4.1.3 | NVD |
References
- https://github.com/fastify/fast-uri/security/advisories/GHSA-5jgf-p345-68v8vendor-advisory, mitigation
- https://cna.openjsf.org/security-advisories.htmlvendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.