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CVE

CVE-2026-27730

esm.sh has SSRF localhost/private-network bypass in `/http(s)` module route
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CVE

CVE-2026-27730

esm.sh has SSRF localhost/private-network bypass in `/http(s)` module route

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.

Package Versions Affected

Package Version
patch Availability
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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
7.5
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
C
H
U
8.6
-
3.0
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
C
H
U
-

Related Resources

No items found.

References

https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27730.json, https://github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4r, https://nvd.nist.gov/vuln/detail/CVE-2026-27730

Severity

8.6

CVSS Score
0
10

Basic Information

Ecosystem
Base CVSS
8.6
EPSS Probability
0.00064%
EPSS Percentile
0.20105%
Introduced Version
0
Fix Available

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