What’s Vulnerable › Vulnerabilities

CVE-2026-44593: esm.sh: Legacy Route Path Traversal Can Lead to RCE

• Severity: high (CVSS 8.7 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% 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, the legacy router first retrieves a response from legacyServer, parses the incoming request path, and ultimately writes the data to storage via buildStorage.Put. The router concatenates the path components without sanitizing them, producing a storage key. When this key is used, the underlying file system resolves the relative segments and writes the file to the specified path. Thus an attacker can craft a request that writes data to arbitrary locations on the server.

Affected products

• esm-dev esm.sh: through 137

References

• https://github.com/esm-dev/esm.sh/security/advisories/GHSA-3636-h3vx-6465
• https://github.com/esm-dev/esm.sh/security/advisories/GHSA-3636-h3vx-6465

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