High · CVSS 7.5CVE-2026-102657

esm.sh: web.NewHandler allows arbitrary file read via encoded dot-segment path traversalCVE-2026-102657

Answer in brief

CVE-2026-102657 records a High severity (CVSS 7.5) vulnerability in esm.sh: web.NewHandler allows arbitrary file read via encoded dot-segment path traversal. The current sources do not mark it as known exploited. The current feed maps esm-dev/esm.sh (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Nov 6, 2026Updated Nov 6, 2026Source checked Nov 6, 2026First seen by HOL Nov 6, 2026Material review Nov 6, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps esm-dev/esm.sh (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
esm-dev/esm.shgeneric	<137_7	137_7

Recommended response

Check inventory. Check lockfiles and deployed manifests for esm-dev/esm.sh.
Review the reported fix. Update esm-dev/esm.sh to 137_7 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Nov 6, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Nov 6, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Nov 6, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.