CVE-2026-86251

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 v3 5.9 MEDIUM

5.9^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.2 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
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

Configurations

No configuration.

History

No history.

Information

Published : 2026-09-06 12:17

Updated : 2026-09-09 14:17

NVD link : CVE-2026-86251

Mitre link : CVE-2026-86251

CVE.ORG link : CVE-2026-86251

JSON object : View

Products Affected

No product.

CWE

CWE-22

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

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