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.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:NI:LA:N3.7/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:NOther