CVE-2026-33490
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.
How to fix
- h32.0.1-rc.17 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| h3 h3 | 2.0.1 | — |
| h3npm | 2.0.1-alpha.0 ≤ v < 2.0.1-rc.17 | 2.0.1-rc.17 |
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