CVE-2026-27730

HIGH

7.5

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.

CVE Details

CVSS v3.1 Score7.5

SeverityHIGH

CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack VectorNETWORK

ComplexityLOW

Privileges RequiredNONE

User InteractionNONE

Published2/25/2026

Last Modified2/27/2026

Sourcenvd

Honeypot Sightings0

Affected Products

esm:esm.sh

Weaknesses (CWE)

CWE-918

References

https://github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4r(security-advisories@github.com)

IOC Correlations

No correlations recorded

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