fast-uri up to 2.4.6/3.1.7/4.1.4 comparison

Summaryinfo

A vulnerability categorized as critical has been discovered in fast-uri up to 2.4.6/3.1.7/4.1.4. Affected by this vulnerability is an unknown functionality. The manipulation results in comparison. This vulnerability was named CVE-2026-86472. The attack may be performed from remote. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in fast-uri up to 2.4.6/3.1.7/4.1.4. Affected is an unknown functionality. The manipulation with an unknown input leads to a comparison vulnerability. CWE is classifying the issue as CWE-697. The product compares two entities in a security-relevant context, but the comparison is incorrect, which may lead to resultant weaknesses. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

fast-uri is a dependency-free RFC 3986 URI parser for Node.js, used by Fastify and ajv. In versions before 2.4.7, from 3.0.0 through 3.1.7, and from 4.0.0 through 4.1.4, fast-uri folds the host to lowercase before it percent-decodes the host, so a percent-encoded uppercase octet such as %41 decodes to a literal A that is never folded. For a scheme-relative reference such as //host there is no scheme, so the host canonicalization that would normally repair this does not run, and parse, normalize, and equal then disagree on the same host. An application that makes a case-sensitive host decision on fast-uri output, for example a host allowlist or denylist that compares the parsed host or uses equal, can be steered past the check with a percent-encoded uppercase octet, and because hostnames are case-insensitive in DNS and HTTP the evading spelling still reaches the host the check meant to gate. The issue is fixed in fast-uri 2.4.7, 3.1.8, and 4.1.5, and users should upgrade to one of those versions or later. As a workaround, compare hosts case-insensitively by lowercasing the parsed host before any allowlist or denylist decision.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-86472 since 09/07/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. The technical details are unknown and an exploit is not available.

Upgrading to version 2.4.7, 3.1.8 or 4.1.5 eliminates this vulnerability.

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Productinfo

Name

• fast-uri

Version

• 2.4.0
• 2.4.1
• 2.4.2
• 2.4.3
• 2.4.4
• 2.4.5
• 2.4.6
• 3.1.0
• 3.1.1
• 3.1.2
• 3.1.3
• 3.1.4
• 3.1.5
• 3.1.6
• 3.1.7
• 4.1.0
• 4.1.1
• 4.1.2
• 4.1.3
• 4.1.4

CPE 2.3info

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CPE 2.2info

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