CVE-2026-42091

Description

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.

CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

EPSS — Exploit Prediction

0.0002

Probability of exploitation

0.03%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-352 Cross-Site Request Forgery

Affected Products

Vendor	Product	Versions
goshs	goshs	< 2.0.2

References

Advisories & Patches

https://github.com/patrickhener/goshs/commit/0e715b94e10c3d1aa552276000f15f104dee2f32 https://github.com/patrickhener/goshs/security/advisories/GHSA-rhf7-wvw3-vjvm https://github.com/patrickhener/goshs/security/advisories/GHSA-rhf7-wvw3-vjvm

Exploits

https://github.com/patrickhener/goshs/security/advisories/GHSA-rhf7-wvw3-vjvm https://github.com/patrickhener/goshs/security/advisories/GHSA-rhf7-wvw3-vjvm

Other References

https://github.com/patrickhener/goshs/releases/tag/v2.0.2

Frequently Asked Questions

What is CVE-2026-42091? +

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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-42091? +

CVE-2026-42091 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0002, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-42091? +

CVE-2026-42091 affects products from goshs, specifically: goshs. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-42091? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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