CVE-2026-86253 PUBLISHED

h3 before 1.15.6 Path Traversal via Percent-Encoded Dot Segments

Assigner: VulnCheck
Reserved: 06.09.2026 Published: 06.09.2026 Updated: 06.09.2026

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.

CVSS Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
CVSS Score: 8.2

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	None
Attack Complexity	High	Integrity	None	Integrity	None
Attack Requirements	Present	Availability	None	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS Score: 5.9

Attack Vector	Network	Scope	Unchanged
Attack Complexity	High	Confidentiality Impact	High
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	h3js
Product	h3
Versions	Default: unaffected affected from 0 to 1.15.6 (excl.) Version 1.15.6 is unaffected affected from 2.0.0-beta.0 to 2.0.1-rc.15 (excl.) Version 2.0.1-rc.15 is unaffected

Credits

0xkakash1 reporter

References

Problem Types

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