{"cve":"CVE-2026-86251","nvd":{"published":"2026-09-06T12:17:15.900","modified":"2026-09-09T14:17:21.977","status":"Awaiting Analysis","description":"h3 versions before 1.15.9 contain a path traversal vulnerability in the serveStatic utility. A double-decoding flaw allows a request path containing double-encoded dot sequences (e.g. %252e%252e) to be decoded to %2e%2e, which survives resolveDotSegments() because that function only checks for literal '.' characters. When the resulting asset ID is resolved by URL-based backends (CDN, S3, object storage), %2e%2e is interpreted as '..' per RFC 3986, enabling path traversal to read arbitrary files from the backend.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","score":8.2},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N","score":5.9},"cwes":["CWE-22"],"references":["https://github.com/h3js/h3/security/advisories/GHSA-72gr-qfp7-vwhw","https://www.vulncheck.com/advisories/h3-before-1.15.9-path-traversal-via-double-decoding","https://github.com/h3js/h3/security/advisories/GHSA-72gr-qfp7-vwhw"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:52:03.409947763+00:00"},"epss":{"cve":"CVE-2026-86251","score":0.00428,"percentile":0.3705,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-72gr-qfp7-vwhw","url":"https://osv.dev/vulnerability/GHSA-72gr-qfp7-vwhw","summary":"h3: Double Decoding in `serveStatic` Bypasses `resolveDotSegments` Path Traversal Protection via `%252e%252e`","modified":"2026-09-10T03:50:37.806165140Z","packages":[{"ecosystem":"npm","name":"h3","purl":"pkg:npm/h3","ranges":["<1.15.9"],"fixed":["1.15.9"]}]}],"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."]}