fast-uri vulnerable to host confusion via skipped IDN canonicalization on scheme-relative references
Summary
| CVE | CVE-2026-75931 |
|---|---|
| State | PUBLISHED |
| Assigner | openjs |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-24 10:16:40 UTC |
| Updated | 2026-09-02 14:44:52 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from ce714d77-add3-4f53-aff5-83d477b104bb
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS: 0.002470000 probability, percentile 0.158620000 (date 2026-08-30)
Problem Types: CWE-436 | CWE-436 CWE-436: Interpretation Conflict
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | ce714d77-add3-4f53-aff5-83d477b104bb | Secondary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
| 3.1 | CNA | CVSS | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
HighAvailability
NoneCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Fast-uri | Fast-uri | affected 2.4.2 2.4.5 semver | Not specified |
| CNA | Fast-uri | Fast-uri | unaffected 2.4.5 semver | Not specified |
| CNA | Fast-uri | Fast-uri | affected 3.1.3 3.1.6 semver | Not specified |
| CNA | Fast-uri | Fast-uri | unaffected 3.1.6 semver | Not specified |
| CNA | Fast-uri | Fast-uri | affected 4.0.1 4.1.3 semver | Not specified |
| CNA | Fast-uri | Fast-uri | unaffected 4.1.3 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| cna.openjsf.org/security-advisories.html | ce714d77-add3-4f53-aff5-83d477b104bb | cna.openjsf.org | Vendor Advisory |
| github.com/fastify/fast-uri/security/advisories/GHSA-5jgf-p345-68v8 | ce714d77-add3-4f53-aff5-83d477b104bb | github.com | Vendor Advisory, Mitigation |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: baeseungwon1010 (en)
CNA: mcollina (en)
CNA: UlisesGascon (en)
There are currently no legacy QID mappings associated with this CVE.