CVE-2026-33131

CRITICAL EPSS 30.7%
Published Mar 20, 20263mo ago · Modified Jun 17, 20262w ago
9.1 CVSS 3.1
Critical
Find Similar
Published Mar 20, 2026 3mo ago
Last Modified Jun 17, 2026 2w ago

Description

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.

CVSS Details

Base Score
9.1
Exploitability
3.9
Impact
5.2
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality High
Integrity High
Availability None

Threat Intelligence

EPSS Exploit Probability
30.7% percentile
Exploit & Patch Status
Public Exploit Known
No Patch Available

Weaknesses 1

CWE-290

Affected Products 14

VendorProductVersionRange
h3h32.0.0any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any
h3h32.0.1any

References 1

  • github.com https://github.com/h3js/h3/security/advisories/GHSA-3vj8-jmxq-cgj5
    ExploitVendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.