Path Traversal in Esm-Dev Esm.sh
CVE-2026-102657
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.
Vulnerability class: Path Traversal (Directory Traversal)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Esm-Dev Esm.sh — versions < 137_7
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-102657?
- CVE-2026-102657 is a high-severity vulnerability in Esm-Dev Esm.sh, classified under Path Traversal. CVSS score: 7.5/10. Published 2026-11-06.
- How severe is CVE-2026-102657?
- High severity. CVSS v3 base score is 7.5 out of 10.