CVE-2026-33131 (GCVE-0-2026-33131)

Vulnerability from cvelistv5 – Published: 2026-03-20 10:16 – Updated: 2026-03-20 11:25
VLAI
Title
h3 has a middleware bypass with one gadget
Summary
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.
Severity
7.4 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
SSVC
Exploitation: poc Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-03-20 11:25 UTC
CWE
  • CWE-290 - Authentication Bypass by Spoofing
Assigner
GitHub_M CNA
References
Impacted products
Vendor Product Version
h3js h3 Affected: >= 2.0.0-0, < 2.0.1-rc.15
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