GHSA-6vgg-xhvh-38ff nebula-mesh: POST /api/v1/hosts/{id}/mobile-bundle response lacks Cache-Control: no-store

Not scored Published 12 Jun 2026

Missing cache-control headers on a mobile bundle API endpoint allow intermediaries to cache and leak freshly generated X25519 private keys.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is GHSA-6vgg-xhvh-38ff?

GHSA-6vgg-xhvh-38ff is a vulnerability in github.com/juev/nebula-mesh, published on 12 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

internal/api/mobile_bundle.go:62-66 sets only Content-Type: application/yaml. The Web-UI sibling at internal/web/handlers.go:1316-1321 sets Cache-Control: no-store, Pragma: no-cache, Expires: 0, X-Content-Type-Options: nosniff — and has a test asserting it. The API path was missed.

Affected

All released versions up to v0.3.0.

Threat model

The endpoint returns a freshly minted X25519 private key inline. Without no-store, any intermediary proxy or CDN that caches 200 OK YAML responses retains the private key for its cache TTL. Same applies to browser disk cache for direct API hits. Combined with the cross-tenant authz advisory (critical), even a corrected authz layer would still leak via cache after fix.

Suggested fix

Copy the four headers from the Web sibling:

w.Header().Set(&#34;Content-Type&#34;, &#34;application/yaml; charset=utf-8&#34;)
w.Header().Set(&#34;Cache-Control&#34;, &#34;no-store&#34;)
w.Header().Set(&#34;Pragma&#34;, &#34;no-cache&#34;)
w.Header().Set(&#34;Expires&#34;, &#34;0&#34;)
w.Header().Set(&#34;X-Content-Type-Options&#34;, &#34;nosniff&#34;)

Mirrors internal/web/handlers.go:1316-1321. Add a parallel test to the existing web-side coverage.

Suggested patch

Verified locally: go vet, go test -race -count=1 ./..., golangci-lint v2.12 all clean.

diff --git a/internal/api/mobile_bundle.go b/internal/api/mobile_bundle.go
index fc09da0..73152eb 100644
--- a/internal/api/mobile_bundle.go
+++ b/internal/api/mobile_bundle.go
@@ -58,8 +58,15 @@ func (s *Server) handleMobileBundle(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Return YAML bundle with proper content-type
+	// Return YAML bundle with proper content-type. The bundle inlines a
+	// freshly-minted X25519 private key, so suppress every layer of cache
+	// between server and operator (intermediate proxies/CDNs, browser disk
+	// cache). Mirrors the Web-UI sibling at internal/web/handlers.go.
 	w.Header().Set(&#34;Content-Type&#34;, &#34;application/yaml; charset=utf-8&#34;)
+	w.Header().Set(&#34;Cache-Control&#34;, &#34;no-store&#34;)
+	w.Header().Set(&#34;Pragma&#34;, &#34;no-cache&#34;)
+	w.Header().Set(&#34;Expires&#34;, &#34;0&#34;)
+	w.Header().Set(&#34;X-Content-Type-Options&#34;, &#34;nosniff&#34;)
 	w.WriteHeader(http.StatusOK)
 	if _, err := w.Write(bundle); err != nil {
 		s.logger.Error(&#34;write mobile bundle response&#34;, &#34;error&#34;, err)
diff --git a/internal/api/mobile_bundle_test.go b/internal/api/mobile_bundle_test.go
index dcb8cd9..da08b01 100644
--- a/internal/api/mobile_bundle_test.go
+++ b/internal/api/mobile_bundle_test.go
@@ -52,6 +52,19 @@ func TestHandleMobileBundle_Success(t *testing.T) {
 		t.Errorf(&#34;Content-Type = %q, want &#39;application/yaml; charset=utf-8&#39;&#34;, ct)
 	}
 
+	// Bundle inlines a private key — every cache between server and operator
+	// must drop the response. Mirrors the Web-UI sibling&#39;s headers.
+	for header, want := range map[string]string{
+		&#34;Cache-Control&#34;:         &#34;no-store&#34;,
+		&#34;Pragma&#34;:                &#34;no-cache&#34;,
+		&#34;Expires&#34;:               &#34;0&#34;,
+		&#34;X-Content-Type-Options&#34;: &#34;nosniff&#34;,
+	} {
+		if got := w.Header().Get(header); got != want {
+			t.Errorf(&#34;%s = %q, want %q&#34;, header, got, want)
+		}
+	}
+
 	// Verify body is valid YAML with expected keys
 	var yamlData map[string]interface{}
 	if err := yaml.Unmarshal(w.Body.Bytes(), &amp;yamlData); err != nil {

Which versions are affected by GHSA-6vgg-xhvh-38ff?

3 open source packages ship an affected version, including github.com/juev/nebula-mesh.

Package	Affected	Fixed in
`github.com/juev/nebula-mesh` Go	All versions	`0.3.2`
`github.com/juev/nebula-mesh` Go	All versions	`0.3.2`
`github.com/juev/nebula-mesh` Go	All versions	`0.3.2`

How do I fix GHSA-6vgg-xhvh-38ff?

Upgrade github.com/juev/nebula-mesh to 0.3.2 or later.

Is GHSA-6vgg-xhvh-38ff being exploited?

There is no known exploitation of GHSA-6vgg-xhvh-38ff in the wild and no public exploit code.

Sources

Also known as GO-2026-5191.