CVE-2026-27730
esm.sh has SSRF localhost/private-network bypass in `/http(s)` module route
- State
- Published
- Severity
- 8.6 High
- Published
- Feb 25, 2026
- Updated
- Feb 25, 2026
- Reserved
- Feb 23, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.0 | 8.6 High | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N | GitHub_M |
Weaknesses
- CWE-918 Server-Side Request Forgery (SSRF)
Affected Products
| Product | Versions |
|---|---|
esm.shesm-dev |
|
References
Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.