esm.sh is a no-build content delivery network (CDN) for web development. Prior to server version 137_7, the documented web.NewHandler static file server in web/handler.go joins the URL-decoded r.URL.Path with Config.AppDir without verifying that the result remains inside the configured application directory. URL-encoded dot segments such as %2e%2e bypass the plain traversal redirect performed by Go's ServeMux, allowing an unauthenticated remote attacker to make the server open and return files outside Config.AppDir that are readable by the server process. The confirmed impact is file disclosure only, and the issue is reachable with Dev disabled. This issue is fixed in server version 137_7.
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History

Fri, 06 Nov 2026 21:00:00 +0000

Type Values Removed Values Added
Description esm.sh is a no-build content delivery network (CDN) for web development. Prior to server version 137_7, the documented web.NewHandler static file server in web/handler.go joins the URL-decoded r.URL.Path with Config.AppDir without verifying that the result remains inside the configured application directory. URL-encoded dot segments such as %2e%2e bypass the plain traversal redirect performed by Go's ServeMux, allowing an unauthenticated remote attacker to make the server open and return files outside Config.AppDir that are readable by the server process. The confirmed impact is file disclosure only, and the issue is reachable with Dev disabled. This issue is fixed in server version 137_7.
Title esm.sh: web.NewHandler allows arbitrary file read via encoded dot-segment path traversal
Weaknesses CWE-22
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-11-06T20:49:28.708Z

Reserved: 2026-09-29T15:56:02.101Z

Link: CVE-2026-102657

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Deferred

Published: 2026-11-06T21:17:05.863

Modified: 2026-11-06T21:17:06.027

Link: CVE-2026-102657

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses