Path Traversal in H3js H3
CVE-2026-86253
h3 (npm package) versions <= 2.0.1-rc.14 contain a path traversal vulnerability in serveStatic(). On Node.js deployments, event.url.pathname is not normalized, so percent-encoded dot segments (%2e%2e) are passed to decodeURI() and decoded to ../ sequences without sanitization. An unauthenticated remote attacker can send crafted requests to endpoints served by serveStatic() to read arbitrary files outside the intended static directory. Fixed in 1.15.6 and 2.0.1-rc.15.
Vulnerability class: Path Traversal (Directory Traversal)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.006 (48.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 48.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.006 · change: +0.002
Affected products
Weakness classification (CWE)
References
- github.com/h3js/h3/security/advisories/GHSA-wr4h-v87w-p3r7 (vendor-advisory)
- www.vulncheck.com/advisories/h3-before-1.15.6-path-traversal-via-percent-encode… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-86253?
- CVE-2026-86253 is a medium-severity vulnerability in H3js H3, classified under Path Traversal. CVSS score: 5.9/10. Published 2026-09-06.
- How severe is CVE-2026-86253?
- Medium severity. CVSS v3 base score is 5.9 out of 10.