CVE-2026-27730 (GCVE-0-2026-27730)

Vulnerability from cvelistv5 – Published: 2026-02-25 15:37 – Updated: 2026-02-25 20:32
VLAI
Title
esm.sh has SSRF localhost/private-network bypass in `/http(s)` module route
Summary
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.
Severity
8.6 (High)
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
SSVC
Exploitation: poc Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-02-25 20:31 UTC
CWE
  • CWE-918 - Server-Side Request Forgery (SSRF)
Assigner
GitHub_M CNA
References
Impacted products
Vendor Product Version
esm-dev esm.sh Affected: <= 137
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