h3js h3 up to 2.0.0-0/2.0.1-rc.14/2.0.1-rc.15 Host event.url/event.url.hostname/event.url._url authentication spoofing

Summaryinfo

A vulnerability, which was classified as critical, has been found in h3js h3 up to 2.0.0-0/2.0.1-rc.14/2.0.1-rc.15. This issue affects some unknown processing of the component Host Handler. Performing a manipulation of the argument event.url/event.url.hostname/event.url._url results in authentication spoofing. This vulnerability is cataloged as CVE-2026-33131. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in h3js h3 up to 2.0.0-0/2.0.1-rc.14/2.0.1-rc.15. It has been classified as critical. This affects an unknown functionality of the component Host Handler. The manipulation of the argument event.url/event.url.hostname/event.url._url with an unknown input leads to a authentication spoofing vulnerability. CWE is classifying the issue as CWE-290. This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

H3 is a minimal H(TTP) framework. Versions 2.0.0-0 through 2.0.1-rc.14 contain a Host header spoofing vulnerability in the NodeRequestUrl (which extends FastURL) which allows middleware bypass. When event.url, event.url.hostname, or event.url._url is accessed, such as in a logging middleware, the _url getter constructs a URL from untrusted data, including the user-controlled Host header. Because H3's router resolves the route handler before middleware runs, an attacker can supply a crafted Host header (e.g., Host: localhost:3000/abchehe?) to make the middleware path check fail while the route handler still matches, effectively bypassing authentication or authorization middleware. This affects any application built on H3 (including Nitro/Nuxt) that accesses event.url properties in middleware guarding sensitive routes. The issue requires an immediate fix to prevent FastURL.href from being constructed with unsanitized, attacker-controlled input. Version 2.0.1-rc.15 contains a patch for this issue.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-33131 since 03/17/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 2.0.1-rc.15 eliminates this vulnerability.

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• h3js

Name

• h3

Version

• 2.0
• 2.0.1-rc.0
• 2.0.1-rc.1
• 2.0.1-rc.2
• 2.0.1-rc.3
• 2.0.1-rc.4
• 2.0.1-rc.5
• 2.0.1-rc.6
• 2.0.1-rc.7
• 2.0.1-rc.8
• 2.0.1-rc.9
• 2.0.1-rc.10
• 2.0.1-rc.11
• 2.0.1-rc.12
• 2.0.1-rc.13
• 2.0.1-rc.14
• 2.0.1-rc.15

Website

• Product: https://github.com/h3js/h3/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion