fast-uri vulnerable to host confusion via backslash authority introducer

Description

fast-uri v4.1.1 and earlier require a literal // to recognize a URI authority, so a reference that uses \\, /\, or \/ as the authority introducer (in place of //, after an optional scheme) is parsed with no authority: the sequence and everything after it fold into the path.

Recommendation

Update the fast-uri package to the latest compatible version. Followings are version details:

• Affected version(s): **>= 4.0.0, < 4.1.2

  >= 3.0.0, < 3.1.5

  < 2.4.4**

• Patched version(s): **4.1.2

  3.1.5

  2.4.4**

References

• GHSA-7p8r-x3mc-p8w7
• cna.openjsf.org
• CVE-2026-18446
• CWE-436
• CAPEC-310
• OWASP 2021-A6

Related Issues

• fast-uri vulnerable to host confusion via literal backslash authority delimiter - CVE-2026-16221
• fast-uri vulnerable to host confusion via percent-encoded authority delimiters - CVE-2026-6322
• fast-uri vulnerable to host confusion via failed IDN canonicalization - CVE-2026-13676
• fast-uri vulnerable to path traversal via percent-encoded dot segments - CVE-2026-6321

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Tags:

npm

fast-uri