What is the CVSS score of CVE-2026-27730?

CVE-2026-27730 has a CVSS 3.1 base score of 7.5 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. EPSS exploitation probability: 0.0%.

Is there a public PoC exploit available for CVE-2026-27730?

Yes, a public proof-of-concept exploit is available for CVE-2026-27730. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-27730?

Within 24 hours: Identify all internal applications and services using esm.sh and assess exposure to the `/http(s)` endpoint; implement network-level access controls to restrict esm.sh from reaching internal systems. Within 7 days: Deploy WAF rules to block suspicious `/http(s)` requests and monitor for exploitation attempts; evaluate alternative CDN providers or maintained esm.sh forks. Within 30 days: Execute migration to patched version once available or alternative CDN solution; conduct forensic review of logs for indicators of compromise.

Esm.Sh CVE-2026-27730

HIGH

Server-Side Request Forgery (SSRF) (CWE-918)

2026-02-25 security-advisories@github.com

GHSA-p2v6-84h2-5x4r

SSRF DNS Esm.Sh Suse Esm Sh Esm

7.5

CVSS 3.1 · GitHub Advisory

View

Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

Access

Craft DNS alias domain resolving to localhost
Delivery

Send request to esm.sh /http(s) route with alias
Exploit

Bypass hostname validation checks
Execution

Server fetches internal service
Impact

Exfiltrate sensitive data

Vulnerability Assessment

Weakness	CWE CWE-918 OWASP Top 10:2025 A01:2025 - Broken Access Control ASVS 5.0 V4 - API and Web Service URL allowlisting, SSRF prevention MITRE ATT&CK 2 techniques across 2 tactics: Initial Access, Credential Access The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Exploitation Conditions	esm.sh versions ≤137 with /http(s) fetch route enabled. Attacker must control or abuse DNS alias domain that resolves to 127.0.0.1 or internal network addresses. No authentication required; default configurations vulnerable to remote exploitation.
Impact	CVSS 7.5 (HIGH). Attack vector: Network. Complexity: Low. Privileges required: None. User interaction: None. Exploitable via remote/network. Public exploit/POC available.
Exploit ScenarioDerived	A remote attacker could exploit this vulnerability to compromise the affected system.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).

Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

esm.sh versions up to 137 contain an SSRF vulnerability in the /http(s) fetch route that allows remote attackers to bypass hostname validation through DNS alias domains and access internal localhost services. Public exploit code exists for this vulnerability, and no patches are currently available. This affects users of esm.sh CDN services and any applications relying on the affected versions.

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 21:55 CVSS 7.5

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. [CVSS 7.5 HIGH]

RemediationAI

Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.

Affected Packages

go github.com/esm-dev/esm.sh fix: 0.0.0-20250616164159-0593516c4cfa

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in go

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Classified as CWE-918 (Server-Side Request Forgery (SSRF)). Affects Esm.Sh. 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.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

GitHub Advisory PRIMARY 7.5 HIGH

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

SUSE 8.6 HIGH

AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Lifecycle Timeline

Patch released

Mar 31, 2026 - 21:13 nvd

Patch available

PoC Detected

Feb 27, 2026 - 17:43 vuln.today

Public exploit code

CVE Published

Feb 25, 2026 - 16:23 nvd

HIGH 7.5

DescriptionGitHub Advisory

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.

Executive ViewAI

Why It Matters

esm.sh, a widely-used CDN for web development, contains a Server-Side Request Forgery (SSRF) vulnerability that could allow attackers to access internal systems and data through the /http(s) fetch route. Organizations using esm.sh versions 137 or earlier are at risk of data exfiltration and lateral movement attacks, with public exploits already available.

Business Impact: High

Compensating Controls

Implement Web Application Firewall (WAF) rules to block /http(s) endpoint requests; isolate esm.sh traffic to network segments with restricted access to internal systems; disable esm.sh fetch functionality if not operationally critical; monitor outbound connections from esm.sh infrastructure for anomalous internal IP targeting; require code review for any esm.sh /http(s) usage; consider temporary removal of esm.sh dependencies pending patch availability.

Threat Intelligence Overview

EPSS Score

0.0%

Top 88% exploitable

Exploit

POC

Public exploit code exists

Data Quality

4 sources

Confidence: Medium

NVD

CVE.org

EPSS Vendor

GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC Yes

EPSS 0.0%

Patch available Yes

Active threat No

Deciding rule

HIGH severity (CVSS 7.0-8.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.