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HIGH

fast-uri vulnerable to host confusion via percent-encoded authority delimiters

Published May 5, 2026

Description

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 products

Remediation

Red Hat statement

This Important flaw in the `fast-uri` library allows an attacker to bypass security controls in Red Hat products that process Uniform Resource Identifiers (URIs). By crafting a malicious URI with percent-encoded authority delimiters, an attacker can cause the library to incorrectly interpret the URI's authority, potentially redirecting applications to an unintended domain. This could lead to a bypass of host allowlist checks, redirect validation, or outbound request routing.

Weaknesses (2)

CWE-140

CWE-436

References (52)

Change history (0)

No recorded changes yet.

Sources
CVE.org / MITRE
Status PUBLISHED
Assigner openjs
Published May 5, 2026
Updated Sep 10, 2026
Reserved Apr 14, 2026
Link CVE-2026-6322
CISA Vulnrichment
Updated May 5, 2026
NVD
Status Modified
Modified Sep 10, 2026
Link CVE-2026-6322
Red Hat
Severity Important
Public date May 5, 2026
Links CVE-2026-6322 - Bugzilla
ENISA EUVD
Assigner openjs
Published May 5, 2026
Updated Sep 10, 2026
Exploited since n/a
Link EUVD-2026-27248
EUVD-2026-27248 GHSA-V39H-62P7-JPJC