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CVE-2026-27730 Details

Description

esm.sh is a no-build content delivery network (CDN) for web development. Versions up to and including 137 have an SSRF vulnerability (CWE-918) in esm.sh’s `/http(s)` fetch route. The service tries to block localhost/internal targets, but the validation is based on hostname string checks and can be bypassed using DNS alias domains. This allows an external requester to make the esm.sh server fetch internal localhost services. As of time of publication, no known patched versions exist.

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:7.5 HIGHVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CNA: [email protected]CVSS-B:8.6 HIGHVector:CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4r	[email protected]	ExploitVendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-918	Server-Side Request Forgery (SSRF)	[email protected]

Affected Products

Product	Versions
esm esm.sh	<= 137
CPE cpe:2.3:a:esm:esm.sh:::::::: Remediation No remediation found in references.

Change History

4 change records found show changes

Date	Action	Recorded By
Jun 17, 2026	CVE Modified	[email protected]
Jun 17, 2026	CVE Modified	CISA-ADP
Feb 27, 2026	Initial Analysis	[email protected]
Feb 25, 2026	New CVE Received	[email protected]