GHSA-6vgg-xhvh-38ff

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

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("Content-Type", "application/yaml; charset=utf-8")
+	w.Header().Set("Cache-Control", "no-store")
+	w.Header().Set("Pragma", "no-cache")
+	w.Header().Set("Expires", "0")
+	w.Header().Set("X-Content-Type-Options", "nosniff")
 	w.WriteHeader(http.StatusOK)
 	if _, err := w.Write(bundle); err != nil {
 		s.logger.Error("write mobile bundle response", "error", 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("Content-Type = %q, want 'application/yaml; charset=utf-8'", ct)
 	}
 
+	// Bundle inlines a private key — every cache between server and operator
+	// must drop the response. Mirrors the Web-UI sibling's headers.
+	for header, want := range map[string]string{
+		"Cache-Control":         "no-store",
+		"Pragma":                "no-cache",
+		"Expires":               "0",
+		"X-Content-Type-Options": "nosniff",
+	} {
+		if got := w.Header().Get(header); got != want {
+			t.Errorf("%s = %q, want %q", header, got, want)
+		}
+	}
+
 	// Verify body is valid YAML with expected keys
 	var yamlData map[string]interface{}
 	if err := yaml.Unmarshal(w.Body.Bytes(), &yamlData); err != nil {