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CVE-2026-27730— esm.sh has SSRF localhost/private-network bypass in `/http(s)` module route

Quick assessment

Affected
esm-dev esm.sh
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

esm.sh是esm.sh开源的一个内容分发网络。 esm.sh 137及之前版本存在代码问题漏洞，该漏洞源于esm.sh的/http(s)获取路由中存在服务端请求伪造漏洞，服务尝试阻止localhost或内部目标，但验证基于主机名字符串检查，可能通过使用DNS别名域被绕过，允许外部请求者使esm.sh服务器获取内部localhost服务。

AI Predicted 9.8 Difficulty: Easy EPSS 0.47% · P39

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-27730

Vulnerability Information
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Vulnerability Title
esm.sh has SSRF localhost/private-network bypass in `/http(s)` module route
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
esm.sh 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
esm.sh是esm.sh开源的一个内容分发网络。 esm.sh 137及之前版本存在代码问题漏洞，该漏洞源于esm.sh的/http(s)获取路由中存在服务端请求伪造漏洞，服务尝试阻止localhost或内部目标，但验证基于主机名字符串检查，可能通过使用DNS别名域被绕过，允许外部请求者使esm.sh服务器获取内部localhost服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
esm-dev esm.sh <= 137 -

II. Public POCs for CVE-2026-27730

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III. Intelligence Information for CVE-2026-27730

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Vendor Advisories for CVE-2026-27730 (1)

IV. Related Vulnerabilities

Same product: esm.sh
Same vendor: esm-dev
Same weakness: CWE-918

V. Comments for CVE-2026-27730

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