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Description

H3 is a minimal H(TTP) framework. In versions 2.0.0-0 through 2.0.1-rc.16, the `mount()` method in h3 uses a simple `startsWith()` check to determine whether incoming requests fall under a mounted sub-application's path prefix. Because this check does not verify a path segment boundary (i.e., that the next character after the base is `/` or end-of-string), middleware registered on a mount like `/admin` will also execute for unrelated routes such as `/admin-public`, `/administrator`, or `/adminstuff`. This allows an attacker to trigger context-setting middleware on paths it was never intended to cover, potentially polluting request context with unintended privilege flags. Version 2.0.2-rc.17 contains a patch.

PUBLISHED Reserved 2026-03-20 | Published 2026-03-26 | Updated 2026-03-26 | Assigner GitHub_M




LOW: 3.7CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Problem types

CWE-706: Use of Incorrectly-Resolved Name or Reference

Product status

>= 2.0.1-alpha.0, < 2.0.1-rc.17
affected

References

github.com/h3js/h3/security/advisories/GHSA-2j6q-whv2-gh6w exploit

github.com/h3js/h3/security/advisories/GHSA-2j6q-whv2-gh6w

cve.org (CVE-2026-33490)

nvd.nist.gov (CVE-2026-33490)

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