{"id":"CVE-2026-33490","summary":"h3: Missing Path Segment Boundary Check in `mount()` Causes Middleware Execution on Unrelated Prefix-Matching Routes","details":"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.","aliases":["GHSA-2j6q-whv2-gh6w"],"modified":"2026-04-02T13:27:32.821277Z","published":"2026-03-26T17:19:15.956Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-706"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33490.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33490.json"},{"type":"ADVISORY","url":"https://github.com/h3js/h3/security/advisories/GHSA-2j6q-whv2-gh6w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33490"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/h3js/h3","events":[{"introduced":"0"},{"fixed":"388b8f06e060a219d11bbc6be7f70f38d8bbea01"}],"database_specific":{"versions":[{"introduced":"2.0.1-alpha.0"},{"fixed":"2.0.1-rc.17"}]}}],"versions":["v0.0.1","v0.0.10","v0.0.11","v0.0.12","v0.0.13","v0.0.14","v0.0.15","v0.0.2","v0.0.3","v0.0.4","v0.0.5","v0.0.6","v0.0.7","v0.0.8","v0.0.9","v0.2.0","v0.2.1","v0.2.10","v0.2.11","v0.2.12","v0.2.2","v0.2.3","v0.2.4","v0.2.5","v0.2.6","v0.2.7","v0.2.8","v0.2.9","v0.3.0","v0.3.1","v0.3.2","v0.3.3","v0.3.4","v0.3.5","v0.3.6","v0.3.7","v0.3.8","v0.3.9","v0.4.0","v0.4.1","v0.4.2","v0.5.0","v0.5.1","v0.5.2","v0.5.3","v0.5.4","v0.5.5","v0.5.6","v0.5.7","v0.6.0","v0.7.0","v0.7.1","v0.7.10","v0.7.11","v0.7.12","v0.7.13","v0.7.14","v0.7.15","v0.7.16","v0.7.17","v0.7.18","v0.7.19","v0.7.2","v0.7.20","v0.7.21","v0.7.3","v0.7.4","v0.7.5","v0.7.6","v0.7.7","v0.7.8","v0.7.9","v0.8.0","v0.8.1","v0.8.2","v0.8.3","v0.8.4","v0.8.5","v0.8.6","v1.0.0","v1.0.1","v1.0.2","v1.1.0","v1.10.0","v1.10.1","v1.10.2","v1.11.0","v1.11.1","v1.12.0","v1.13.0","v1.13.1","v1.14.0","v1.15.0","v1.15.1","v1.15.10","v1.15.11","v1.15.2","v1.15.3","v1.15.4","v1.15.5","v1.15.6","v1.15.7","v1.15.8","v1.15.9","v1.2.0","v1.2.1","v1.3.0","v1.4.0","v1.5.0","v1.6.0","v1.6.1","v1.6.2","v1.6.3","v1.6.4","v1.6.5","v1.6.6","v1.7.0","v1.7.1","v1.8.0","v1.8.0-rc.0","v1.8.0-rc.1","v1.8.0-rc.2","v1.8.0-rc.3","v1.8.1","v1.8.2","v1.9.0","v2.0.0-beta.0","v2.0.0-beta.1","v2.0.0-beta.2","v2.0.0-beta.3","v2.0.0-beta.4","v2.0.0-beta.5","v2.0.0-rc.1","v2.0.1-rc.10","v2.0.1-rc.11","v2.0.1-rc.12","v2.0.1-rc.13","v2.0.1-rc.14","v2.0.1-rc.15","v2.0.1-rc.16","v2.0.1-rc.2","v2.0.1-rc.3","v2.0.1-rc.4","v2.0.1-rc.5","v2.0.1-rc.6","v2.0.1-rc.7","v2.0.1-rc.8","v2.0.1-rc.9"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33490.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}