CVE-2026-27730

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 v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact NONE

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4r	Exploit Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:esm:esm.sh:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-02-25 16:23

Updated : 2026-02-27 17:43

NVD link : CVE-2026-27730

Mitre link : CVE-2026-27730

CVE.ORG link : CVE-2026-27730

JSON object : View

Products Affected

esm

esm.sh

CWE

CWE-918

Server-Side Request Forgery (SSRF)

{"id": "CVE-2026-27730", "cveTags": [], "metrics": {"cvssMetricV30": [{"type": "Secondary", "source": "security-advisories@github.com", "cvssData": {"scope": "CHANGED", "version": "3.0", "baseScore": 8.6, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 4.0, "exploitabilityScore": 3.9}], "cvssMetricV31": [{"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.5, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}, "impactScore": 3.6, "exploitabilityScore": 3.9}]}, "published": "2026-02-25T16:23:27.123", "references": [{"url": "https://github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4r", "tags": ["Exploit", "Vendor Advisory"], "source": "security-advisories@github.com"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Primary", "source": "security-advisories@github.com", "description": [{"lang": "en", "value": "CWE-918"}]}], "descriptions": [{"lang": "en", "value": "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\u2019s `/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."}, {"lang": "es", "value": "esm.sh es una red de entrega de contenido (CDN) sin compilaci\u00f3n para desarrollo web. Las versiones hasta la 137 inclusive tienen una vulnerabilidad SSRF (CWE-918) en la ruta de obtenci\u00f3n '/http(s)' de esm.sh. El servicio intenta bloquear objetivos localhost/internos, pero la validaci\u00f3n se basa en comprobaciones de cadenas de nombres de host y puede ser eludida usando dominios alias de DNS. Esto permite que un solicitante externo haga que el servidor de esm.sh obtenga servicios internos de localhost. Hasta el momento de la publicaci\u00f3n, no existen versiones parcheadas conocidas."}], "lastModified": "2026-02-27T17:43:47.737", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:esm:esm.sh:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "AD6FA8D1-421D-416D-98EE-9DD8B7C02AAB", "versionEndIncluding": "137"}], "operator": "OR"}]}], "sourceIdentifier": "security-advisories@github.com"}