fast-uri vulnerable to inconsistent host case normalization via percent-encoded octets — GHSA-HRR3-GC8F-F4QJ

Summary

### Impact `fast-uri` folds the host to lowercase before it percent-decodes the host, so a percent-encoded uppercase unreserved octet such as `%41` decodes to a literal `A` that is never folded. For a scheme-relative reference (`//host`) there is no scheme, so the host canonicalization that repairs this on a scheme-bearing URL does not run. As a result `parse`, `normalize`, and `equal` disagree on the same host:…

Timeline

Published by source

2026-09-29

Risk context

• Reported severity or threat level: medium.
• Reported CVSS score: 4.8 out of 10.
• Reported EPSS value: 0.00253.
• Review exposure for the affected product or family: npm: fast-uri.

Product

npm: fast-uri

What to do

General, cautious steps (verify details in the official source):

• Review exposure and plan remediation based on risk and environment.
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-HRR3-GC8F-F4QJ

Source

GitHub

Vendor

GitHub

Published by source

2026-09-29

Last source activity

2026-09-29

Additional identifiers

CVE-2026-86472

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.