CVE-2026-33490
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.
- Score
- CVSS 3.1 5.3 Medium
- Status
- Analyzed - security-advisories@github.com
- Published
- 2026-03-26
- Last modified
- 2026-03-26
- Weaknesses
- CWE-706
Affected products
References
- https://github.com/h3js/h3/security/advisories/GHSA-2j6q-whv2-gh6w
