5.5

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2025-59342

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

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.

(GitHub Advisory)

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CVE-2025-59342

CVE-2025-59342:

5.5

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/esm-dev/esm.sh	go	<= 136

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability lies in the handling of the X-Zone-Id header within the esmRouter function in server/router.go. The provided commit 833a29f42aeb0acbd7089a71be11dd0a292d3151 clearly shows the fix for this path traversal vulnerability. The patch modifies the esmRouter function to validate the X-Zone-Id header before it's used in normalizeSavePath to construct a file path. Previously, the raw header value was used, allowing an attacker to use ../ to traverse the directory structure and write files outside the intended directory. The esmRouter function is the central point where the malicious input is processed, making it the vulnerable function that would appear in a runtime profile during exploitation of this vulnerability.

Vulnerable functions

Only Mi**o us*rs **n s** t*is s**tion

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WAF Protection Rules

WAF Rule

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Reasoning

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