CVE-2026-27730: esm.sh is a no-build content delivery network (CDN) for web development

Q: How do I fix CVE-2026-27730?

esm.sh: upgrade to newer than 137. Exact commands for each OS are on this page.

Q: Is CVE-2026-27730 being exploited?

CVE-2026-27730 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-27730 affect?

CVE-2026-27730 affects esm.sh. Severity is high (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. The service tries to block localhost/internal targets, but th

Q: How urgent is CVE-2026-27730?

Priority 44/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2026-27730 is a high-severity flaw (CVSS 7.5) affecting esm.sh. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 publicat

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 67%)
CISA exploited list	No
Weakness	CWE-918
Published	2026-02-25
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: esm

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-02-25 16:23 UTCPublished CVE record published
2026-06-17 10:27 UTCUpdated Record last modified

esm esm.sh UPGRADE

Affected: <= 137

Fixed in: newer than 137

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy esm.sh || rpm -q esm.sh || esm.sh --version

2. UPGRADE to newer than 137 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade esm.sh

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade esm.sh

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-27730?

esm.sh: upgrade to newer than 137. Exact commands for each OS are on this page.

Is CVE-2026-27730 being exploited?

CVE-2026-27730 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-27730 affect?

CVE-2026-27730 affects esm.sh. Severity is high (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. The service tries to block localhost/internal targets, but th

How urgent is CVE-2026-27730?

Priority 44/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2025-65025 HIGH 8.2 UPGRADE esm.sh is a nobuild content delivery network(CDN) for modern web development
CVE-2025-65026 MEDIUM 6.1 UPGRADE esm.sh is a nobuild content delivery network(CDN) for modern web development
CVE-2026-23644 HIGH 7.5 UPGRADE esm.sh is a no-build content delivery network (CDN) for web development
CVE-2025-50180 HIGH 7.5 UPGRADE esm.sh is a no-build content delivery network (CDN) for web development

References

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