CVE-2026-27730 | THREATINT

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.

PUBLISHED Reserved 2026-02-23 | Published 2026-02-25 | Updated 2026-02-25 | Assigner GitHub_M

HIGH: 8.6CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

Problem types

CWE-918: Server-Side Request Forgery (SSRF)

Product status

<= 137

affected

References

github.com/...esm.sh/security/advisories/GHSA-p2v6-84h2-5x4r

cve.org (CVE-2026-27730)

nvd.nist.gov (CVE-2026-27730)

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