CVE-2026-86251 — h3 before 1.15.9 Path Traversal via Double Decoding
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…
Published: 2026-09-06 · CVSS: 8.2 · CVSS 4.0
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7