CVE-2026-27730
Versions up to and including 137 have an SSRF vulnerability (CWE-918) in esm.sh’s `/http(s)` fetch route.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.34%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- EPSS
- 0.34% probability · 27th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-918
- Affected
- esm/esm.sh
- Source
- security-advisories@github.com
References
- https://github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4rExploit, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.