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Fencer Vulns
medium 6.5

CVE-2026-42091 json

goshs has Cross-Origin Arbitrary File Write via Missing CSRF on PUT and Wildcard CORS

published 2026-04-23 6 mo ago modified 2026-10-26 13 d ago also EUVD-2026-27067 , GHSA-rhf7-wvw3-vjvm , GO-2026-5625

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 5%
public exploits
0
none known

Summary

goshs is a SimpleHTTPServer written in Go. Prior to version 2.0.2, the PUT upload handler (httpserver/updown.go) lacks the CSRF token validation that was added to the POST upload handler during the CVE-2026-40883 fix. Combined with the unconditional Access-Control-Allow-Origin: * on the OPTIONS preflight handler (httpserver/server.go), any website can write arbitrary files to a goshs instance through the victim's browser — bypassing network isolation (e.g. localhost, internal network). This issue has been patched in version 2.0.2.

Patch / fix

  • go github.com/patrickhener/goshs/v2 2.0.2
  • go goshs.de/goshs/v2 2.0.2
  • goshs goshs 2.0.2
  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/patrickhener/goshs/security/advisories/GHSA-rhf7-wvw3-vjvm referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
GitHub 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
go github.com/patrickhener/goshs/v2
<2.0.2
2.0.2
go github.com/patrickhener/goshs
<=1.1.4
all versions
 no fix listed
go goshs.de/goshs
all versions
 no fix listed
go goshs.de/goshs/v2
<2.0.2
2.0.2

Affected products

  • patrickhener goshs

Classification

Weakness
  • CWE-352 Cross-Site Request Forgery

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.