fast-uri vulnerable to host confusion via percent-encoded scheme normalization — GHSA-JQFF-G426-HQXP

Summary

### Impact `fast-uri` decodes percent-encoded characters in the scheme component with the legacy global `unescape()` and serializes the result back as raw characters, without re-escaping it or validating it as a scheme. A scheme that decodes to characters outside the RFC 3986 scheme grammar can therefore introduce structure the original input did not contain. For example, `%2f%2fevil.example:/pwn` parses with no…

Timeline

Published by source

2026-09-02

Risk context

• Reported severity or threat level: high.
• Reported CVSS score: 7.5 out of 10.
• Reported EPSS value: 0.00247.
• 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):

• Prioritize patching or mitigation immediately (treat as actively risky).
• 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-JQFF-G426-HQXP

Source

GitHub

Vendor

GitHub

Published by source

2026-09-02

Last source activity

2026-09-02

Additional identifiers

CVE-2026-76172

Curated by

hlukh.ch

Related advisories and connections

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