CVE-2026-44593: esm-dev esm.sh Path Traversal

Vulnerability summary

CVE-2026-44593 is a high (CVSS 8.7) Path Traversal vulnerability in esm-dev esm.sh. EPSS estimates a 0.50% chance of exploitation in the next 30 days, higher than 41.2% of scored vulnerabilities.

Timeline

1. 28-05-2026
   PublishedVulnerability first disclosed.
2. 02-06-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.