GHSA-4c8g-83qw-93j6

Suggest an improvement
Source
https://github.com/advisories/GHSA-4c8g-83qw-93j6
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-4c8g-83qw-93j6/GHSA-4c8g-83qw-93j6.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-4c8g-83qw-93j6
Aliases
Downstream
Published
2026-07-21T19:03:11Z
Modified
2026-09-11T15:45:36Z
Severity
  • 7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N CVSS Calculator
Summary
fast-uri vulnerable to host confusion via failed IDN canonicalization
Details

Impact

fast-uri versions >= 2.3.1, <= 4.0.0 fail to canonicalize Unicode/IDN hostnames for HTTP-family URLs. The IDN conversion path calls URL.domainToASCII(...) on the global WHATWG URL constructor, where that helper does not exist. The resulting TypeError is silently routed into parsed.error, but parse(), normalize(), and equal() all return with the host left in its original Unicode form.

For example, http://127。0。0。1/ is treated by fast-uri as host 127。0。0。1, while Node's WHATWG URL parser and fetch() canonicalize the same input to 127.0.0.1.

Applications that use fast-uri to enforce host-based policy (denylists, loopback filtering, redirect validation, outbound proxy routing) before passing the same URL into Node's URL or fetch() consumers see a policy/use desync and can be steered to an unintended destination.

Patches

Upgrade to fast-uri v4.0.1, v3.1.3, or v2.4.2

Workarounds

None. Upgrade to the patched version.

Database specific 
{
    "cwe_ids": [
        "CWE-436",
        "CWE-551"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-21T19:03:11Z",
    "nvd_published_at": "2026-06-29T14:16:47Z",
    "severity": "HIGH"
}
References

Affected packages

npm / fast-uri

Package

Name
fast-uri
View open source insights on deps.dev
Purl
pkg:npm/fast-uri

Affected ranges

Type
SEMVER
Events
Introduced
4.0.0
Fixed
4.0.1

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-4c8g-83qw-93j6/GHSA-4c8g-83qw-93j6.json"

npm / fast-uri

Package

Name
fast-uri
View open source insights on deps.dev
Purl
pkg:npm/fast-uri

Affected ranges

Type
SEMVER
Events
Introduced
3.0.0
Fixed
3.1.3

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-4c8g-83qw-93j6/GHSA-4c8g-83qw-93j6.json"

npm / fast-uri

Package

Name
fast-uri
View open source insights on deps.dev
Purl
pkg:npm/fast-uri

Affected ranges

Type
SEMVER
Events
Introduced
2.3.1
Fixed
2.4.2

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-4c8g-83qw-93j6/GHSA-4c8g-83qw-93j6.json"