How severe is CVE-2026-27730?

CVE-2026-27730 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-27730 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-27730?

CVE-2026-27730 affects Esm Esm.sh. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-27730?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-27730 have an EU (EUVD) identifier?

Yes. CVE-2026-27730 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-8685.

When was CVE-2026-27730 published?

CVE-2026-27730 was published on 2026-02-25 and last updated on 2026-06-17.

CVE-2026-27730

CVE-2026-27730 is a high-severity vulnerability in Esm Esm.sh with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-918.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (26th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-8685
Weakness: CWE-918
Affected product: Esm Esm.sh
Published: 2026-02-25
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-27730?: CVE-2026-27730 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-27730 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-27730?: CVE-2026-27730 affects Esm Esm.sh. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-27730?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-27730 have an EU (EUVD) identifier?: Yes. CVE-2026-27730 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-8685.
When was CVE-2026-27730 published?: CVE-2026-27730 was published on 2026-02-25 and last updated on 2026-06-17.

References

https://github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4r

Affected products (1)

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

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