CVE-2026-6322 — fast-uri vulnerable to host confusion via percent-encoded authority delimiters

Description (CNA)

fast-uri normalize() decoded percent-encoded authority delimiters inside the host component and then re-emitted them as raw delimiters during serialization. A host that combined an allowed domain, an encoded at-sign, and a different domain was re-emitted with the at-sign as a raw userinfo separator, changing the URI's authority to the second domain. Applications that normalize untrusted URLs before host allowlist checks, redirect validation, or outbound request routing can be steered to a different authority than the input appeared to specify. Versions <= 3.1.1 are affected. Update to 3.1.2 or later.

Affected (CNA)

Vendor / product	Versions
fast-uri / fast-uri	affected 0 before 3.1.2; unaffected 3.1.2

CWE

CWE-436

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.

redhat-SADP

A flaw was found in fast-uri. A remote attacker could exploit this vulnerability by crafting a malicious Uniform Resource Identifier (URI) that contains percent-encoded authority delimiters. The fast-uri library incorrectly decodes these delimiters during normalization and then re-emits them as raw separators, which can change the URI's intended authority. This issue allows applications that perform host allowlist checks, redirect validation, or outbound request routing to be steered to a different authority than specified, potentially bypassing security controls.