NIST deprecates RSA-2048 from 2030. Find every one of them before attackers do.
🛡️
Not in CISA KEV
HIGH severity

CVE-2026-102657 — Esm-dev

HIGHFix: esm-dev/esm.sh@468b6b2

CVE-2026-102657 is a high-severity (CVSS 7.5) Path Traversal vulnerability. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

esm.sh is a no-build content delivery network (CDN) for web development. Prior to server version 137_7, the documented web.NewHandler static file server in web/handler.go joins the…

Published
Updated
Affected
—
Patched
See advisory
Exploits
None indexed
Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs54th percentile — riskier than 54% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Description

esm.sh is a no-build content delivery network (CDN) for web development. Prior to server version 137_7, the documented web.NewHandler static file server in web/handler.go joins the URL-decoded r.URL.Path with Config.AppDir without verifying that the result remains inside the configured application directory. URL-encoded dot segments such as %2e%2e bypass the plain traversal redirect performed by Go's ServeMux, allowing an unauthenticated remote attacker to make the server open and return files outside Config.AppDir that are readable by the server process. The confirmed impact is file disclosure only, and the issue is reachable with Dev disabled. This issue is fixed in server version 137_7.

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Remediation status

    The records we use list no fixed release for CVE-2026-102657. Check the upstream advisory for a patched version, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Frequently Asked Questions

esm.sh is a no-build content delivery network (CDN) for web development. Prior to server version 137_7, the documented web.NewHandler static file server in web/handler.go joins the URL-decoded r.URL.Path with Config.AppDir without verifying that the result remains inside the configured application directory. URL-encoded dot segments such as %2e%2e bypass the plain traversal redirect performed by Go's ServeMux, allowing an unauthenticated remote attacker to make the server open and return files outside Config.AppDir that are readable by the server process. The confirmed impact is file disclosur
O3 Security · Impact-Aware SCA

Is CVE-2026-102657 in your dependencies?

Find it across your dependency tree, including transitive dependencies.

Scan my dependencies How O3 SCA works