What’s Vulnerable › Vulnerabilities

CVE-2026-86253: h3 before 1.15.6 Path Traversal via Percent-Encoded Dot Segments

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-06 · updated 2026-09-10
• Weakness: CWE-22

Description

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.

Affected products

• h3js h3: before 1.15.6; from 2.0.0-beta.0 before 2.0.1-rc.15 — fixed in 1.15.6, 2.0.1-rc.15

How to fix

Upgrade to a fixed version: h3js h3 1.15.6, 2.0.1-rc.15. Check the vendor advisory for mitigations.

References

• https://github.com/h3js/h3/security/advisories/GHSA-wr4h-v87w-p3r7
• https://www.vulncheck.com/advisories/h3-before-1.15.6-path-traversal-via-percent-encoded-dot-segments

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