Description
fast-uri percent-decodes the scheme component with the legacy global unescape() before validating it, so an input whose decoded scheme is a valid but dangerous token is emitted as a live scheme. RFC 3986 section 3.
Recommendation
Update the fast-uri package to the latest compatible version. Followings are version details:
Affected version(s): **>= 4.0.0, < 4.2.3 >= 3.0.0, < 3.1.9 < 2.4.8** Patched version(s): **4.2.3 3.1.9 2.4.8**
References
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- fast-uri vulnerable to host confusion via percent-encoded scheme normalization - CVE-2026-76172
- fast-uri vulnerable to host confusion via percent-encoded authority delimiters - CVE-2026-6322
- fast-uri vulnerable to mailto header injection via percent-encoded field-name desynchronization - CVE-2026-86818
- fast-uri vulnerable to inconsistent host case normalization via percent-encoded octets - CVE-2026-86472
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See something that needs correcting? Let us knowUpdated October 23, 2026