{"cve":"CVE-2026-33490","nvd":{"published":"2026-03-26T18:16:30.237","modified":"2026-06-17T10:37:35.357","status":"Analyzed","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","score":5.3},"cwes":["CWE-706"],"references":["https://github.com/h3js/h3/security/advisories/GHSA-2j6q-whv2-gh6w","https://github.com/h3js/h3/security/advisories/GHSA-2j6q-whv2-gh6w"],"products":["h3:h3"],"source":"nvd","synced_at":"2026-10-19T22:28:18.033120106+00:00"},"epss":{"cve":"CVE-2026-33490","score":0.00248,"percentile":0.16161,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-2j6q-whv2-gh6w","url":"https://osv.dev/vulnerability/GHSA-2j6q-whv2-gh6w","summary":"h3: Missing Path Segment Boundary Check in `mount()` Causes Middleware Execution on Unrelated Prefix-Matching Routes","modified":"2026-03-27T21:16:22.484306Z","packages":[{"ecosystem":"npm","name":"h3","purl":"pkg:npm/h3","ranges":[">=2.0.1-alpha.0 <2.0.1-rc.17"],"fixed":["2.0.1-rc.17"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}