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Fencer Vulns
medium 5.5

CVE-2025-59342 json

esm.sh writes arbitrary files via path traversal in `X-Zone-Id` header

published 2025-09-17 13 mo ago modified 2026-09-10 1 mo ago also EUVD-2025-29764 , GHSA-g2h5-cvvr-7gmw , GO-2025-3967

cvss
5.5
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
3.2%
EPSS 3.2% chance of exploitation in 30 days, percentile 88%
public exploits
1
Exploit-DB, plus a Nuclei check

Summary

esm.sh is a nobuild content delivery network(CDN) for modern web development. In 136 and earlier, a path-traversal flaw in the handling of the X-Zone-Id HTTP header allows an attacker to cause the application to write files outside the intended storage location. The header value is used to build a filesystem path but is not properly canonicalized or restricted to the application’s storage base directory. As a result, supplying ../ sequences in X-Zone-Id causes files to be written to arbitrary directories. Version 136.1 contains a patch.

Patch / fix

  • go github.com/esm-dev/esm.sh 136.1
  • govulncheck-vulndb SLE Module for Package Hub 15 SP6, openSUSE Leap 15.6 0.0.20251023T162509-150000.1.110.1

suse advisories SUSE-SU-2025:3799-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
  • govulncheck-vulndb openSUSE Tumbleweed 0.0.20250924T192141-1.1

opensuse advisories openSUSE-SU-2026:21483-1openSUSE-SU-2025:15576-1

Timeline

  1. Published
  2. First public exploit (EDB-52461)

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
13 mo ago

Exploit prediction

3.15% chance of exploitation in the next 30 days, higher than 88% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • EDB-52461 esm-dev 136 - Path Traversal webapps, 2025-12-16
  • Nuclei template esm.sh <= v136 - Arbitrary File Write via Path Traversal nuclei detection template

CVSS scores

assigned by version score vector
CNA 4.0 5.5 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
CNA 4.0 5.5 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/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

Affected packages

ecosystem package affected fixed in
go github.com/esm-dev/esm.sh
<136.1
all versions
136.1

Affected products

  • esm-dev esm.sh

Classification

Weakness
  • CWE-24 Path Traversal: '../filedir'

References

Sources

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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.