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CVE-2026-44593

HIGHCVSS 8.7/10EPSS 0.36%

Last modified

CVE-2026-44593 is a high-severity vulnerability rated 8.7/10 on the CVSS scale. 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. EPSS estimates a 0.36% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 4.0
8.7/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability
0.36%

28.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

References

Timeline

Published
Last Modified
Status
Deferred

Frequently Asked Questions

What is CVE-2026-44593?
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.
How severe is CVE-2026-44593?
CVE-2026-44593 has a CVSS score of 8.7/10 (HIGH severity). The EPSS model estimates a 0.36% probability of exploitation in the next 30 days.
How do I fix CVE-2026-44593?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-44593?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST