CVE-2026-44593: Esm-Dev Esm.sh

High severity, CVSS 8.7. EPSS: 0.5% chance of exploitation in the next 30 days.

esm.sh is a no-build content delivery network (CDN) for web development. In 137 and earlier, the legacy router first retrieves a response from legacyServer, parses the incoming request path, and ultimately writes the data to storage via buildStorage.Put. The router concatenates the path components without sanitizing them, producing a storage key. When this key is used, the underlying file system resolves the relative segments and writes the file to the specified path. Thus an attacker can craft a request that writes data to arbitrary locations on the server.

Affected products

• Esm-Dev Esm.sh: up to and including 137

Published 2026-05-28. Last modified 2026-06-17.