CVE-2026-27730
February 25, 2026
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.
Affected Packages
https://github.com/esm-dev/esm.sh.git (GITHUB):
Affected version(s) >=v34 <v136_1Fix Suggestion:
Update to version v136_1github.com/esm-dev/esm.sh (GO):
Affected version(s) >=v0.0.0-20240514002037-19735e27aaf9 <v0.0.0-20250616164159-0593516c4cfaFix Suggestion:
Update to version v0.0.0-20250616164159-0593516c4cfaRelated Resources (6)
Do you need more information?
Contact UsCVSS v4
Base Score:
9.2
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
NONE
Vulnerable System Availability
NONE
Subsequent System Confidentiality
HIGH
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
8.6
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Weakness Type (CWE)
Server-Side Request Forgery (SSRF)
EPSS
Base Score:
0.04
