CVE-2026-44594: esm.sh: Path Traversal via package.json browser field allows reading arbitrary server files

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-28 · updated 2026-10-26
Weakness: CWE-22

Description

esm.sh is a no-build content delivery network (CDN) for web development. In 137 and earlier, a Local File Inclusion (LFI) vulnerability exists in the esbuild plugin's handling of the browser field in package.json. An attacker can publish an npm package that causes the server to read and return arbitrary files from the host filesystem during the build process.

Affected products

esm-dev esm.sh: through 137

References

https://github.com/esm-dev/esm.sh/security/advisories/GHSA-rg65-45m7-hq57
https://github.com/esm-dev/esm.sh/security/advisories/GHSA-rg65-45m7-hq57

Get alerted when CVE-2026-44594 or the next vulnerability affects your stack