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CVE-2026-27730

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CVE-2026-27730

Published: Feb 25, 2026

Modified: Feb 25, 2026

PUBLISHED

CVSS v3.0

8.6

HIGH

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.

VendorProductVersions

esm-dev

esm.sh

affected
<= 137

Weaknesses (CWE)

CWE-918

CVSS v3.0 Details

CVSS v3.0 Vector

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

None

Availability

None

References

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