VULNERABILITY INTELLIGENCE

CVE-2026-27730

CVSS score7.5 HIGH
EPSS probability0.39%
CISA KEVNot currently listed
Published2026-02-25
Last modified2026-06-17
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

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.

Weakness classification

  • security-advisories@github.com: CWE-918

Primary references