diff --git a/app/Console/Commands/PollMetrics.php b/app/Console/Commands/PollMetrics.php
index 58c58dd..d5c82b0 100644
--- a/app/Console/Commands/PollMetrics.php
+++ b/app/Console/Commands/PollMetrics.php
@@ -36,10 +36,22 @@ class PollMetrics extends Command
         $clients = [];
 
         do {
-            $servers = Server::has('credential')->get();
+            // Only servers with a PRESENT, non-disabled credential. A credential disabled
+            // between ticks drops the server here, so its cached connection is no longer polled
+            // (the vault refuses a fresh connect, but a reused long-lived session would not
+            // re-check disabled_at). Prune any cached client whose server just left the set so
+            // the revoked server's open session is closed promptly, not left idle until exit.
+            $servers = Server::withActiveCredential()->get();
+            $activeIds = $servers->pluck('id')->all();
+            foreach (array_keys($clients) as $id) {
+                if (! in_array($id, $activeIds, true)) {
+                    $clients[$id]->disconnect();
+                    unset($clients[$id]);
+                }
+            }
 
             if ($servers->isEmpty()) {
-                $this->warn('Keine Server mit Credential — nichts zu pollen.');
+                $this->warn('Keine Server mit aktivem Credential — nichts zu pollen.');
             }
 
             foreach ($servers as $server) {
diff --git a/app/Models/Server.php b/app/Models/Server.php
index ed2aa6e..21965d1 100644
--- a/app/Models/Server.php
+++ b/app/Models/Server.php
@@ -2,6 +2,7 @@
 
 namespace App\Models;
 
+use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\HasOne;
 use Illuminate\Support\Str;
@@ -30,4 +31,15 @@ class Server extends Model
     {
         return $this->hasOne(SshCredential::class);
     }
+
+    /**
+     * Servers whose stored SSH credential is present AND not disabled — the live poll set.
+     * A disabled ("gesperrt") credential is refused by CredentialVault::resolve() at connect
+     * time, but the poller reuses a long-lived connection, so revocation only takes effect if
+     * the server also drops OUT of this query on the next tick.
+     */
+    public function scopeWithActiveCredential(Builder $query): void
+    {
+        $query->whereHas('credential', fn (Builder $q) => $q->whereNull('disabled_at'));
+    }
 }
diff --git a/docker-compose.prod.yml b/docker-compose.prod.yml
index 154f129..29a8716 100644
--- a/docker-compose.prod.yml
+++ b/docker-compose.prod.yml
@@ -23,6 +23,15 @@ x-image: &image
     APP_DEBUG: "false"
   networks:
     - clusev
+  # Defense-in-depth (applies to app/reverb/queue/scheduler via <<: *image). no-new-privileges
+  # blocks privilege escalation through setuid binaries — the image's drop-privileges startup only
+  # LOWERS privileges, so it stays compatible. pids_limit is a fork-bomb backstop, set generously so
+  # php-fpm/queue workers never hit it under normal load. cap_drop:[ALL] and read_only are
+  # deliberately NOT set here: they need a per-service prod smoke test first (nginx :80 bind needs
+  # NET_BIND_SERVICE, php-fpm/nginx/supervisor write pid/sockets/logs), so enable them after testing.
+  security_opt:
+    - "no-new-privileges:true"
+  pids_limit: 1024
 
 services:
   app:
@@ -97,6 +106,9 @@ services:
       APP_INTERNAL_URL: "http://app:80"
     expose:
       - "3000"
+    security_opt:
+      - "no-new-privileges:true"
+    pids_limit: 512
     networks:
       - clusev
 
@@ -113,8 +125,10 @@ services:
       # Domain is dashboard-driven via on-demand TLS (Caddy asks app:/_caddy/ask), so
       # no SITE_ADDRESS is needed. Only the ACME contact comes from .env.
       ACME_EMAIL: "${ACME_EMAIL:-admin@localhost}"
-      # External reverse-proxy TLS: set to the upstream proxy's CIDR so Caddy trusts
-      # its X-Forwarded-Proto. Leave as 127.0.0.1/32 when Caddy terminates TLS itself.
+      # External reverse-proxy TLS: set to the upstream proxy's EXACT address (a /32, or its
+      # tightest CIDR) so Caddy trusts its X-Forwarded-Proto/-For. Leave as 127.0.0.1/32 when
+      # Caddy terminates TLS itself. SECURITY: never a broad range / 0.0.0.0/0 — a too-wide value
+      # lets any client forge X-Forwarded-For and defeat the IP-keyed throttles + brute-force ban.
       TRUSTED_PROXY_CIDR: "${TRUSTED_PROXY_CIDR:-127.0.0.1/32}"
     volumes:
       # Mount the DIRECTORY (not the single Caddyfile): a single-file bind mount keeps the
@@ -124,6 +138,9 @@ services:
       - ./docker/caddy:/etc/caddy:ro
       - caddy-data:/data      # ACME account + certs — MUST persist across recreate
       - caddy-config:/config
+    security_opt:
+      - "no-new-privileges:true"
+    pids_limit: 512
     depends_on:
       - app
       - reverb
@@ -147,6 +164,9 @@ services:
       interval: 10s
       timeout: 5s
       retries: 30
+    security_opt:
+      - "no-new-privileges:true"
+    pids_limit: 1024
     networks:
       - clusev
     # no host ports in prod — DB is reachable only on the internal clusev network
@@ -158,6 +178,9 @@ services:
     command: redis-server --appendonly yes --requirepass "${REDIS_PASSWORD:?set REDIS_PASSWORD in .env}"
     volumes:
       - redis-data:/data
+    security_opt:
+      - "no-new-privileges:true"
+    pids_limit: 512
     networks:
       - clusev
 
diff --git a/docker/caddy/Caddyfile b/docker/caddy/Caddyfile
index 07fd505..6abfa07 100644
--- a/docker/caddy/Caddyfile
+++ b/docker/caddy/Caddyfile
@@ -26,7 +26,12 @@
 	auto_https disable_redirects
 
 	# Honor X-Forwarded-* from a trusted upstream proxy (external-TLS mode). Defaults to
-	# 127.0.0.1/32 (trust nothing external); set TRUSTED_PROXY_CIDR to the proxy's address.
+	# 127.0.0.1/32 (trust nothing external); set TRUSTED_PROXY_CIDR to the upstream proxy's
+	# EXACT address (a /32, or its tightest CIDR). SECURITY: never a broad range and never
+	# 0.0.0.0/0 — a too-wide value lets any client forge X-Forwarded-For, which then drives
+	# request()->ip() in the app and defeats the IP-keyed login/2FA throttles + the honeypot
+	# brute-force ban (an attacker can spoof a victim's IP to get it banned, or a whitelisted
+	# IP to evade the ban entirely).
 	servers {
 		trusted_proxies static {$TRUSTED_PROXY_CIDR:127.0.0.1/32}
 	}
diff --git a/tests/Feature/PollMetricsCredentialTest.php b/tests/Feature/PollMetricsCredentialTest.php
new file mode 100644
index 0000000..7034adb
--- /dev/null
+++ b/tests/Feature/PollMetricsCredentialTest.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Models\Server;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Tests\TestCase;
+
+/**
+ * The metrics poller keeps one long-lived SSH connection per server and reuses it across
+ * ticks. CredentialVault::resolve() enforces a credential's `disabled_at` lock only at
+ * connect() time, so a connection opened BEFORE a credential is disabled would keep pulling
+ * metrics over the already-open session. The poll set must therefore exclude servers whose
+ * credential is disabled (or missing) at the query, so a revoked credential drops out of the
+ * live loop on the next tick — Server::withActiveCredential() is that gate.
+ */
+class PollMetricsCredentialTest extends TestCase
+{
+    use RefreshDatabase;
+
+    private function serverWithCredential(string $name, string $ip, ?string $disabledAt): Server
+    {
+        $server = Server::create(['name' => $name, 'ip' => $ip, 'ssh_port' => 22, 'status' => 'online']);
+        $server->credential()->create([
+            'username' => 'root',
+            'auth_type' => 'password',
+            'secret' => 'x',
+            'disabled_at' => $disabledAt,
+        ]);
+
+        return $server;
+    }
+
+    public function test_only_servers_with_an_active_credential_are_pollable(): void
+    {
+        $enabled = $this->serverWithCredential('enabled', '10.0.0.1', null);
+        $disabled = $this->serverWithCredential('disabled', '10.0.0.2', now()->toDateTimeString());
+        $noCredential = Server::create(['name' => 'bare', 'ip' => '10.0.0.3', 'ssh_port' => 22, 'status' => 'online']);
+
+        $ids = Server::withActiveCredential()->pluck('id');
+
+        $this->assertTrue($ids->contains($enabled->id));       // enabled credential → polled
+        $this->assertFalse($ids->contains($disabled->id));     // disabled (revoked) credential → excluded
+        $this->assertFalse($ids->contains($noCredential->id)); // no credential → excluded
+    }
+}