CVE-2026-27730: esm-dev esm.sh Server-Side Request Forgery (SSRF)
Vulnerability summary
CVE-2026-27730 is a high (CVSS 8.6) Server-Side Request Forgery (SSRF) vulnerability in esm-dev esm.sh. EPSS estimates a 0.48% chance of exploitation in the next 30 days, higher than 40.3% of scored vulnerabilities. 1 public exploit is recorded.
Advisory lineage
Upstream 0 · Downstream 2 · Related 2Timeline
- 25-02-2026PublishedVulnerability first disclosed.
- 25-02-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
4 scores · 3 sources · 2 versions- OSV · GoEcosystem advisory · calculated8.6HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
- NVDNIST8.6HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
EPSS trend
Probability
0.48%
Chance of exploitation in the next 30 days
Percentile
40%
Versus all other CVEs
30-day change
+0.15 pp
From 0.34% on 18-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundEsm.Sh
Maturity: poc
Weaknesses
CWE · root causeAffected systems
Esm1 product
- esm.sh≤ 137
Esm-dev1 product
- esm.sh≤ 137
Github.com/esm-dev1 product
- esm.sh< 0.0.0-20250616164159-0593516c4cfa
3 vendors · 3 products
References
6 links- github.com/esm-dev/esm.sh/security/advisories/GHSA-p2v6-84h2-5x4rX Refsource CONFIRMWEBAdvisoryExploitVendor Advisory
- github.com/esm-dev/esm.shPACKAGE