CVE-2025-59342 MEDIUM

CVE-2025-59342: esm.sh writes arbitrary files via path traversal in `X-Zone-Id` header

Vendor Esm-Dev
Product esm.sh
Weakness CWE-24
Published September 17, 2025
Last update January 14, 2026

CVSS base score

5.5/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

September 17, 2025 CVE published
January 14, 2026 Record updated