CVE-2026-86251
h3 before 1.15.9 Path Traversal via Double Decoding
CVSS Score
5.9
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-22 |
| Vendor | h3js |
| Product | h3 |
| Published | Sep 6, 2026 |
| Last Updated | Sep 9, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None
Affected Versions
h3js / h3
0 < 1.15.9
References
Credits
🔍 offset