CVE-2026-42091 | goshs has Cross-Origin Arbitrary File Write via Missing CSRF on PUT and Wildcard CORS

Exp

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.

Published: 2026-05-04 Last update: 2026-05-12 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-42091 is rated Exploit Available (50/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.17%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-42091

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-42091

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.01% 0.17% +0.15%
2 2026-05-05 — 0.01% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-42091

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 3.6 [email protected]

Weakness enumeration for CVE-2026-42091

GitHub Security Advisory for CVE-2026-42091

GHSA-rhf7-wvw3-vjvm · Severity: medium · Ecosystem: go — goshs has Cross-Origin Arbitrary File Write via Missing CSRF on PUT and Wildcard CORS

Affected software / configurations for CVE-2026-42091

Vendor Product Version Raw CPE
goshs goshs < 2.0.2 cpe:2.3:a:goshs:goshs:*:*:*:*:*:go:*:*

References for CVE-2026-42091

cvelogic Threat Intelligence