diff --git a/admin.go b/admin.go
index b367975de..b8b4cebf9 100644
--- a/admin.go
+++ b/admin.go
@@ -940,7 +940,9 @@ func (h adminHandler) handleError(w http.ResponseWriter, r *http.Request, err er
 // rebinding attacks.
 func (h adminHandler) checkHost(r *http.Request) error {
 	allowed := slices.ContainsFunc(h.allowedOrigins, func(u *url.URL) bool {
-		return r.Host == u.Host
+		// Host comparison is case-insensitive per RFC 3986 §3.2.2, same as
+		// the Origin check below; url.Parse does not normalize host case.
+		return strings.EqualFold(r.Host, u.Host)
 	})
 	if !allowed {
 		return APIError{
diff --git a/admin_checkhost_case_test.go b/admin_checkhost_case_test.go
new file mode 100644
index 000000000..98204e336
--- /dev/null
+++ b/admin_checkhost_case_test.go
@@ -0,0 +1,83 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddy
+
+import (
+	"net/http/httptest"
+	"net/url"
+	"testing"
+)
+
+// TestAdminHandlerCheckHostCaseInsensitive is the regression test for the
+// Host allow-list comparison being case-sensitive. Per RFC 3986 §3.2.2,
+// host names are case-insensitive, and url.Parse does not normalize host
+// case, so the comparison must fold case. This mirrors the fix applied to
+// originAllowed, where an allowed 'http://Example.com:8080' rejected a
+// client Host of 'example.com:8080'.
+func TestAdminHandlerCheckHostCaseInsensitive(t *testing.T) {
+	mustParse := func(raw string) *url.URL {
+		u, err := url.Parse(raw)
+		if err != nil {
+			t.Fatalf("invalid URL %q: %v", raw, err)
+		}
+		return u
+	}
+
+	cases := []struct {
+		name    string
+		allowed *url.URL
+		host    string
+		wantErr bool
+	}{
+		{
+			name:    "allow-list uppercase, request Host lowercase",
+			allowed: mustParse("http://Example.com:2019"),
+			host:    "example.com:2019",
+			wantErr: false,
+		},
+		{
+			name:    "allow-list lowercase, request Host uppercase",
+			allowed: mustParse("http://example.com:2019"),
+			host:    "EXAMPLE.com:2019",
+			wantErr: false,
+		},
+		{
+			name:    "default localhost entry, request Host uppercase",
+			allowed: mustParse("http://localhost:2019"),
+			host:    "LOCALHOST:2019",
+			wantErr: false,
+		},
+		{
+			name:    "different host is still rejected",
+			allowed: mustParse("http://example.com:2019"),
+			host:    "evil.example.org:2019",
+			wantErr: true,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			h := adminHandler{allowedOrigins: []*url.URL{tc.allowed}}
+			r := httptest.NewRequest("GET", "http://"+tc.host+"/config/", nil)
+			err := h.checkHost(r)
+			if tc.wantErr && err == nil {
+				t.Errorf("checkHost(%q) with allowed %v = nil, want error", tc.host, tc.allowed)
+			}
+			if !tc.wantErr && err != nil {
+				t.Errorf("checkHost(%q) with allowed %v = %v, want nil", tc.host, tc.allowed, err)
+			}
+		})
+	}
+}