CVE-2025-59342: Esm-Dev Esm.sh

Medium severity, CVSS 5.5. EPSS: 3% chance of exploitation in the next 30 days.

esm.sh is a nobuild content delivery network(CDN) for modern web development. In 136 and earlier, a path-traversal flaw in the handling of the X-Zone-Id HTTP header allows an attacker to cause the application to write files outside the intended storage location. The header value is used to build a filesystem path but is not properly canonicalized or restricted to the application’s storage base directory. As a result, supplying ../ sequences in X-Zone-Id causes files to be written to arbitrary directories. Version 136.1 contains a patch.

Affected products

• Esm-Dev Esm.sh: up to and including 136

Published 2025-09-17. Last modified 2026-06-17.