Summary
goshs: WebDAV listener ignores --read-only, --upload-only, and --no-delete mode flags
WebDAV listener ignores --read-only, --upload-only, and --no-delete mode flags
Ecosystem: Go
Package: goshs.de/goshs/v2 (github.com/patrickhener/goshs)
Affected: <= v2.0.9 (every release that ships the WebDAV handler)
When goshs is launched with WebDAV enabled (-w), the mode-restriction flags --read-only, --upload-only, and --no-delete are enforced only on the primary HTTP port. The WebDAV port is wired straight to golang.org/x/net/webdav.Handler with no equivalent guard, so an authenticated WebDAV client can PUT, DELETE, MKCOL, MOVE, and COPY despite the operator's stated intent.
Details
httpserver/server.go:207-238, the WebDAV mux registers only IPWhitelistMiddleware, ServerHeaderMiddleware, and optionally BasicAuthMiddleware. There is no fs.ReadOnly || fs.UploadOnly || fs.NoDelete check on the WebDAV path. The HTTP mux in the same file (lines 134-204) does check these flags on every state-changing route.
Proof of concept
mkdir -p /tmp/r && echo secret > /tmp/r/x.txt
goshs -p 18000 -wp 18001 -w -ro -d /tmp/r -b admin:pw &
curl -u admin:pw -X PUT http://localhost:18000/y.txt --data x # 403 (HTTP enforces -ro)
curl -u admin:pw -X PUT http://localhost:18001/y.txt --data x # 201 (WebDAV writes anyway)
curl -u admin:pw -X DELETE http://localhost:18001/x.txt # 204 (WebDAV deletes anyway)
curl -u admin:pw -X MKCOL http://localhost:18001/pwned/ # 201 (WebDAV creates dir)
Impact
- Integrity,
--read-onlyand--no-deleteare silently downgraded to "no protection" on the WebDAV port. Any WebDAV client (curl, cadaver, Windows Explorer, Finder) can overwrite/delete files. - Confidentiality,
--upload-onlyis also bypassed: WebDAV GET/PROPFIND still return file contents. - Trust, operators using
goshs -w -ro -d /srv/case-files -b reviewer:pwto deliver engagement artifacts believe the directory is immutable. It isn't.
CVE-2026-50138 has a CVSS score of 8.1 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.1.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Add a small http.HandlerFunc in front of wdHandler that maps WebDAV verbs to the existing mode flags:
wdGuard := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
switch r.Method {
case http.MethodPut, "MKCOL", "MOVE", "COPY":
if fs.ReadOnly || fs.UploadOnly { http.Error(w, "read-only", 403); return }
case http.MethodDelete:
if fs.ReadOnly || fs.UploadOnly || fs.NoDelete { http.Error(w, "delete disabled", 403); return }
case http.MethodGet, "PROPFIND", "HEAD":
if fs.UploadOnly { http.Error(w, "upload-only", 403); return }
}
wdHandler.ServeHTTP(w, r)
})
Add regression tests in integration/functions.go covering each mode flag × each WebDAV verb.
Reporter: Nishant Verma. Reproduced live against goshs v2.0.9 (commit 8fc1e91) on 2026-05-27.
Frequently Asked Questions
- What is CVE-2026-50138? CVE-2026-50138 is a high-severity security vulnerability in goshs.de/goshs/v2 (go), affecting versions <= 2.0.9. It is fixed in 2.1.0.
- How severe is CVE-2026-50138? CVE-2026-50138 has a CVSS score of 8.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of goshs.de/goshs/v2 are affected by CVE-2026-50138? goshs.de/goshs/v2 (go) versions <= 2.0.9 is affected.
- Is there a fix for CVE-2026-50138? Yes. CVE-2026-50138 is fixed in 2.1.0. Upgrade to this version or later.
- Is CVE-2026-50138 exploitable, and should I be worried? Whether CVE-2026-50138 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-50138 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-50138? Upgrade
goshs.de/goshs/v2to 2.1.0 or later.