CVE-2026-27730
esm.sh has SSRF localhost/private-network bypass in `/http(s)` module route
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.
INFO
Published Date :
Feb. 25, 2026, 4:23 p.m.
Last Modified :
Feb. 27, 2026, 5:43 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.0 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Monitor for vendor-supplied patches or updates.
- Consider network segmentation to limit internal access.
- Implement stricter input validation on fetch requests.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-27730.
| URL | Resource |
|---|---|
| https://github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4r | ExploitVendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-27730 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-27730
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-27730 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-27730 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Feb. 27, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Added CPE Configuration OR *cpe:2.3:a:esm:esm.sh:*:*:*:*:*:*:*:* versions up to (including) 137 Added Reference Type GitHub, Inc.: https://github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4r Types: Exploit, Vendor Advisory -
New CVE Received by [email protected]
Feb. 25, 2026
Action Type Old Value New Value Added 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. Added CVSS V3 AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N Added CWE CWE-918 Added Reference https://github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4r