CVE-2026-102657 json
esm.sh: web.NewHandler allows arbitrary file read via encoded dot-segment path traversal
published 2026-11-06 2 d ago modified 2026-11-06 2 d ago also EUVD-2026-118494
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.7%
- EPSS 0.7% chance of exploitation in 30 days, percentile 54%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- github.com/esm-dev/esm.sh@468b6b2 commit
- github.com/esm-dev/esm.sh@fc3b345 commit
- github.com/esm-dev/esm.sh#1376 pull request
- github.com/esm-dev/esm.sh/releases/tag/v137_7 release
Exploit prediction
0.72% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
Affected products
- esm-dev esm.sh
Classification
- Weakness
-
- CWE-22 Improper Limitation of a Pathname to a Restricted Directory
References
- github.com /esm-dev/esm.sh/pull/1376
- github.com /esm-dev/esm.sh/commit/468b6b2a4b4dfec334cf6b33b01fcd4e5cd93bed
- github.com /esm-dev/esm.sh/commit/fc3b345e73aeaa0b7a05b6f27d91c05fdf5f9b53
- github.com /esm-dev/esm.sh/security/advisories/GHSA-g3c2-rjq2-c763
- github.com /esm-dev/esm.sh/releases/tag/v137_7
Sources
- CVE List CVE-2026-102657
- NVD CVE-2026-102657
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.