diff --git a/.env.example b/.env.example
index b50232a52..6764eb03f 100644
--- a/.env.example
+++ b/.env.example
@@ -4,6 +4,16 @@ APP_KEY=
 APP_DEBUG=false
 APP_URL=http://localhost
 
+# Security: Host Header Injection / Open Redirect hardening (CVE-2025-50578).
+# TRUSTED_PROXIES: comma-separated CIDRs/IPs of reverse proxies allowed to set
+#   X-Forwarded-* headers. Defaults to the private ranges below when unset. Use
+#   "*" to trust all proxies (only behind a trusted network boundary).
+#TRUSTED_PROXIES=192.168.0.0/16,172.16.0.0/12,10.0.0.0/8,127.0.0.1
+# TRUSTED_HOSTS: comma-separated hostnames Heimdall is allowed to serve. Unset
+#   means no restriction (default, backward compatible). Set this to your own
+#   domain to fully prevent host-header injection / open redirects.
+#TRUSTED_HOSTS=heimdall.example.com
+
 APP_LOCALE=en
 APP_FALLBACK_LOCALE=en
 APP_FAKER_LOCALE=en_US
diff --git a/app/Http/Middleware/TrustHosts.php b/app/Http/Middleware/TrustHosts.php
new file mode 100644
index 000000000..cde8d8f43
--- /dev/null
+++ b/app/Http/Middleware/TrustHosts.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use Illuminate\Http\Middleware\TrustHosts as Middleware;
+
+class TrustHosts extends Middleware
+{
+    /**
+     * Get the host patterns that should be trusted.
+     *
+     * The allow-list is read from the TRUSTED_HOSTS env var (comma-separated
+     * hostnames). When it is unset/empty an empty array is returned so that NO
+     * host restriction is applied, preserving Heimdall's historic behaviour of
+     * running on arbitrary hosts. When set, only the listed hosts (and their
+     * subdomains) are accepted; any other Host header is rejected by Symfony
+     * with a SuspiciousOperationException (HTTP 400).
+     *
+     * @return array
+     */
+    public function hosts()
+    {
+        $trustedHosts = env('TRUSTED_HOSTS');
+
+        if ($trustedHosts === null || trim((string) $trustedHosts) === '') {
+            return [];
+        }
+
+        $hosts = [];
+
+        foreach (explode(',', (string) $trustedHosts) as $host) {
+            $host = trim($host);
+
+            if ($host !== '') {
+                $hosts[] = '^(.+\.)?'.preg_quote($host).'$';
+            }
+        }
+
+        return $hosts;
+    }
+
+    /**
+     * Determine if the application should specify trusted hosts.
+     *
+     * The parent implementation skips enforcement whenever the app runs in the
+     * "local" environment (Heimdall's shipped default, see .env.example) or
+     * under the test runner, which would leave the TRUSTED_HOSTS allow-list
+     * silently unenforced for almost every real deployment. Instead we tie
+     * enforcement directly to configuration: apply the allow-list whenever one
+     * has actually been provided, in any environment. When TRUSTED_HOSTS is
+     * unset hosts() is empty and this returns false, preserving the historic
+     * no-restriction behaviour.
+     *
+     * @return bool
+     */
+    protected function shouldSpecifyTrustedHosts()
+    {
+        return ! empty($this->hosts());
+    }
+}
diff --git a/app/Http/Middleware/TrustProxies.php b/app/Http/Middleware/TrustProxies.php
index 95e5ccd77..0de5aa1c5 100644
--- a/app/Http/Middleware/TrustProxies.php
+++ b/app/Http/Middleware/TrustProxies.php
@@ -8,16 +8,52 @@
 class TrustProxies extends Middleware
 {
     /**
-     * The trusted proxies for this application.
+     * The default trusted proxies used when the TRUSTED_PROXIES env var is unset.
      *
      * @var array
      */
-    protected $proxies = ['192.168.0.0/16', '172.16.0.0/12', '10.0.0.0/8', '127.0.0.1'];
+    protected $defaultProxies = ['192.168.0.0/16', '172.16.0.0/12', '10.0.0.0/8', '127.0.0.1'];
+
+    /**
+     * The trusted proxies for this application.
+     *
+     * @var array<int, string>|string|null
+     */
+    protected $proxies;
 
     /**
      * The current proxy header mappings.
      *
-     * @var array
+     * Note: Request::HEADER_X_FORWARDED_HOST is intentionally NOT trusted to
+     * prevent Host header injection / open redirects (CVE-2025-50578). A spoofed
+     * X-Forwarded-Host header must never influence getHost()/url()/asset().
+     *
+     * @var int
      */
-    protected $headers = Request::HEADER_X_FORWARDED_FOR | Request::HEADER_X_FORWARDED_HOST | Request::HEADER_X_FORWARDED_PORT | Request::HEADER_X_FORWARDED_PROTO | Request::HEADER_X_FORWARDED_AWS_ELB;
+    protected $headers = Request::HEADER_X_FORWARDED_FOR | Request::HEADER_X_FORWARDED_PORT | Request::HEADER_X_FORWARDED_PROTO | Request::HEADER_X_FORWARDED_AWS_ELB;
+
+    /**
+     * Create a new middleware instance.
+     *
+     * The set of trusted proxies is read from the TRUSTED_PROXIES env var
+     * (comma-separated CIDRs/IPs). When unset it falls back to the historic
+     * default list. The special value "*" trusts all proxies.
+     *
+     * @return void
+     */
+    public function __construct()
+    {
+        $trustedProxies = env('TRUSTED_PROXIES');
+
+        if ($trustedProxies === null || trim((string) $trustedProxies) === '') {
+            $this->proxies = $this->defaultProxies;
+        } elseif (trim((string) $trustedProxies) === '*') {
+            $this->proxies = '*';
+        } else {
+            $this->proxies = array_values(array_filter(
+                array_map('trim', explode(',', (string) $trustedProxies)),
+                fn ($proxy) => $proxy !== ''
+            ));
+        }
+    }
 }
diff --git a/bootstrap/app.php b/bootstrap/app.php
index 1b6473e0b..4dcefb18c 100644
--- a/bootstrap/app.php
+++ b/bootstrap/app.php
@@ -32,6 +32,9 @@
 
         $middleware->replace(\Illuminate\Http\Middleware\TrustProxies::class, \App\Http\Middleware\TrustProxies::class);
 
+        $middleware->trustHosts();
+        $middleware->replace(\Illuminate\Http\Middleware\TrustHosts::class, \App\Http\Middleware\TrustHosts::class);
+
         $middleware->alias([
             'allowed' => \App\Http\Middleware\CheckAllowed::class,
             'bindings' => \Illuminate\Routing\Middleware\SubstituteBindings::class,
diff --git a/tests/Feature/TrustHostsTest.php b/tests/Feature/TrustHostsTest.php
new file mode 100644
index 000000000..afc1b51e3
--- /dev/null
+++ b/tests/Feature/TrustHostsTest.php
@@ -0,0 +1,146 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Http\Middleware\TrustHosts;
+use Illuminate\Contracts\Http\Kernel;
+use Illuminate\Http\Request;
+use Symfony\Component\HttpFoundation\Exception\SuspiciousOperationException;
+use Tests\TestCase;
+
+class TrustHostsTest extends TestCase
+{
+    /**
+     * Remove any TRUSTED_HOSTS override and reset Symfony's static trusted host
+     * state so tests do not leak into one another.
+     */
+    protected function tearDown(): void
+    {
+        putenv('TRUSTED_HOSTS');
+        unset($_ENV['TRUSTED_HOSTS'], $_SERVER['TRUSTED_HOSTS']);
+
+        Request::setTrustedHosts([]);
+
+        parent::tearDown();
+    }
+
+    private function setTrustedHostsEnv(string $value): void
+    {
+        putenv('TRUSTED_HOSTS='.$value);
+        $_ENV['TRUSTED_HOSTS'] = $value;
+        $_SERVER['TRUSTED_HOSTS'] = $value;
+    }
+
+    private function makeMiddleware(): TrustHosts
+    {
+        return $this->app->make(TrustHosts::class);
+    }
+
+    public function test_hosts_is_empty_when_env_unset(): void
+    {
+        putenv('TRUSTED_HOSTS');
+        unset($_ENV['TRUSTED_HOSTS'], $_SERVER['TRUSTED_HOSTS']);
+
+        $this->assertSame([], $this->makeMiddleware()->hosts());
+    }
+
+    public function test_arbitrary_host_is_accepted_when_env_unset(): void
+    {
+        putenv('TRUSTED_HOSTS');
+        unset($_ENV['TRUSTED_HOSTS'], $_SERVER['TRUSTED_HOSTS']);
+
+        // No trusted host patterns configured -> getHost() must not throw.
+        Request::setTrustedHosts(array_filter($this->makeMiddleware()->hosts()));
+
+        $request = Request::create('http://anything.example/', 'GET');
+
+        $this->assertSame('anything.example', $request->getHost());
+    }
+
+    public function test_hosts_contains_pattern_matching_configured_host(): void
+    {
+        $this->setTrustedHostsEnv('example.com');
+
+        $hosts = $this->makeMiddleware()->hosts();
+
+        $this->assertNotEmpty($hosts);
+        $this->assertCount(1, $hosts);
+        // Symfony wraps each pattern as {pattern}i before matching.
+        $this->assertSame(1, preg_match('{'.$hosts[0].'}i', 'example.com'));
+        $this->assertSame(0, preg_match('{'.$hosts[0].'}i', 'evil.com'));
+    }
+
+    public function test_configured_host_is_accepted_and_others_rejected(): void
+    {
+        $this->setTrustedHostsEnv('example.com');
+
+        Request::setTrustedHosts($this->makeMiddleware()->hosts());
+
+        $accepted = Request::create('http://example.com/', 'GET');
+        $this->assertSame('example.com', $accepted->getHost());
+
+        $this->expectException(SuspiciousOperationException::class);
+
+        Request::create('http://evil.com/', 'GET')->getHost();
+    }
+
+    public function test_multiple_hosts_can_be_configured(): void
+    {
+        $this->setTrustedHostsEnv('example.com, dash.example.org');
+
+        $hosts = $this->makeMiddleware()->hosts();
+
+        $this->assertCount(2, $hosts);
+
+        Request::setTrustedHosts($hosts);
+
+        $this->assertSame('example.com', Request::create('http://example.com/', 'GET')->getHost());
+        $this->assertSame('dash.example.org', Request::create('http://dash.example.org/', 'GET')->getHost());
+    }
+
+    public function test_custom_trust_hosts_middleware_is_registered_globally(): void
+    {
+        $globalMiddleware = $this->app->make(Kernel::class)->getGlobalMiddleware();
+
+        $this->assertContains(TrustHosts::class, $globalMiddleware);
+        $this->assertNotContains(\Illuminate\Http\Middleware\TrustHosts::class, $globalMiddleware);
+    }
+
+    public function test_handle_enforces_trusted_hosts_even_in_local_environment(): void
+    {
+        // The app runs as APP_ENV=local under the test runner; the parent
+        // middleware would skip enforcement entirely. Confirm handle() still
+        // applies the allow-list once TRUSTED_HOSTS is configured.
+        $this->setTrustedHostsEnv('example.com');
+
+        $request = Request::create('http://example.com/', 'GET');
+
+        $reachedNext = false;
+        $this->makeMiddleware()->handle($request, function ($req) use (&$reachedNext) {
+            $reachedNext = true;
+
+            return $req;
+        });
+
+        $this->assertTrue($reachedNext);
+
+        // The configured host is now accepted and any other Host is rejected.
+        $this->assertSame('example.com', Request::create('http://example.com/', 'GET')->getHost());
+
+        $this->expectException(SuspiciousOperationException::class);
+        Request::create('http://evil.com/', 'GET')->getHost();
+    }
+
+    public function test_handle_does_not_restrict_hosts_when_env_unset(): void
+    {
+        putenv('TRUSTED_HOSTS');
+        unset($_ENV['TRUSTED_HOSTS'], $_SERVER['TRUSTED_HOSTS']);
+
+        $request = Request::create('http://anything.example/', 'GET');
+
+        $this->makeMiddleware()->handle($request, fn ($req) => $req);
+
+        // No allow-list configured -> arbitrary hosts still accepted.
+        $this->assertSame('anything.example', Request::create('http://anything.example/', 'GET')->getHost());
+    }
+}
diff --git a/tests/Feature/TrustProxiesTest.php b/tests/Feature/TrustProxiesTest.php
new file mode 100644
index 000000000..bc06ecd70
--- /dev/null
+++ b/tests/Feature/TrustProxiesTest.php
@@ -0,0 +1,108 @@
+<?php
+
+namespace Tests\Feature;
+
+use App\Http\Middleware\TrustProxies;
+use Illuminate\Http\Request;
+use Tests\TestCase;
+
+class TrustProxiesTest extends TestCase
+{
+    /**
+     * Remove any TRUSTED_PROXIES override and reset Symfony's static trusted
+     * proxy/host state so tests do not leak into one another.
+     */
+    protected function tearDown(): void
+    {
+        putenv('TRUSTED_PROXIES');
+        unset($_ENV['TRUSTED_PROXIES'], $_SERVER['TRUSTED_PROXIES']);
+
+        Request::setTrustedProxies([], Request::HEADER_X_FORWARDED_FOR);
+        Request::setTrustedHosts([]);
+
+        parent::tearDown();
+    }
+
+    private function setTrustedProxiesEnv(string $value): void
+    {
+        putenv('TRUSTED_PROXIES='.$value);
+        $_ENV['TRUSTED_PROXIES'] = $value;
+        $_SERVER['TRUSTED_PROXIES'] = $value;
+    }
+
+    private function readProtected(object $object, string $property): mixed
+    {
+        return (fn () => $this->{$property})->call($object);
+    }
+
+    public function test_x_forwarded_host_header_is_ignored(): void
+    {
+        $request = Request::create('http://localhost/', 'GET');
+        $request->server->set('REMOTE_ADDR', '10.0.0.1');
+        $request->headers->set('X-Forwarded-Host', 'evil.com');
+        $request->server->set('HTTP_X_FORWARDED_HOST', 'evil.com');
+
+        (new TrustProxies())->handle($request, fn ($req) => $req);
+
+        $this->assertSame('localhost', $request->getHost());
+        $this->assertNotSame('evil.com', $request->getHost());
+    }
+
+    public function test_headers_bitmask_excludes_forwarded_host(): void
+    {
+        $headers = $this->readProtected(new TrustProxies(), 'headers');
+
+        $this->assertSame(0, $headers & Request::HEADER_X_FORWARDED_HOST);
+        $this->assertNotSame(0, $headers & Request::HEADER_X_FORWARDED_FOR);
+        $this->assertNotSame(0, $headers & Request::HEADER_X_FORWARDED_PORT);
+        $this->assertNotSame(0, $headers & Request::HEADER_X_FORWARDED_PROTO);
+        $this->assertNotSame(0, $headers & Request::HEADER_X_FORWARDED_AWS_ELB);
+    }
+
+    public function test_default_trusted_proxies_when_env_unset(): void
+    {
+        putenv('TRUSTED_PROXIES');
+        unset($_ENV['TRUSTED_PROXIES'], $_SERVER['TRUSTED_PROXIES']);
+
+        $proxies = $this->readProtected(new TrustProxies(), 'proxies');
+
+        $this->assertSame(
+            ['192.168.0.0/16', '172.16.0.0/12', '10.0.0.0/8', '127.0.0.1'],
+            $proxies
+        );
+    }
+
+    public function test_trusted_proxies_can_be_configured_via_env(): void
+    {
+        $this->setTrustedProxiesEnv('203.0.113.5, 198.51.100.0/24');
+
+        $proxies = $this->readProtected(new TrustProxies(), 'proxies');
+
+        $this->assertSame(['203.0.113.5', '198.51.100.0/24'], $proxies);
+    }
+
+    public function test_trusted_proxies_supports_wildcard(): void
+    {
+        $this->setTrustedProxiesEnv('*');
+
+        $proxies = $this->readProtected(new TrustProxies(), 'proxies');
+
+        $this->assertSame('*', $proxies);
+    }
+
+    public function test_wildcard_proxy_trusts_calling_ip_for_forwarded_headers(): void
+    {
+        $this->setTrustedProxiesEnv('*');
+
+        $request = Request::create('http://localhost/', 'GET');
+        $request->server->set('REMOTE_ADDR', '203.0.113.9');
+        $request->headers->set('X-Forwarded-Proto', 'https');
+        $request->server->set('HTTP_X_FORWARDED_PROTO', 'https');
+
+        (new TrustProxies())->handle($request, fn ($req) => $req);
+
+        // Proto is honored (proxy trusted) but host is still not taken from headers.
+        $this->assertTrue($request->isSecure());
+        $this->assertSame('localhost', $request->getHost());
+    }
+}