From b5fb37b939cc3a587d9ae566878786dcdc2c456e Mon Sep 17 00:00:00 2001
From: Liviu-Mihail Concioiu <liviu.concioiu@gmail.com>
Date: Sun, 14 Sep 2025 21:00:21 +0200
Subject: [PATCH] Fix #19570 - Check for HTTP_HOST and document the issue in
 FAQ (#19858)

Fixes #19570

* Check for HTTP_HOST and document the issue in FAQ

Signed-off-by: Liviu-Mihail Concioiu <liviu.concioiu@gmail.com>

* Remove whitespace

Signed-off-by: Liviu-Mihail Concioiu <liviu.concioiu@gmail.com>

* Update libraries/classes/Controllers/HomeController.php

Co-authored-by: William Desportes <williamdes@wdes.fr>

---------

Signed-off-by: Liviu-Mihail Concioiu <liviu.concioiu@gmail.com>
Co-authored-by: William Desportes <williamdes@wdes.fr>
---
 doc/faq.rst                                   | 21 +++++++++++++++++++
 .../classes/Controllers/HomeController.php    | 16 ++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/doc/faq.rst b/doc/faq.rst
index 1cc7d295ec..7d9abad4f1 100644
--- a/doc/faq.rst
+++ b/doc/faq.rst
@@ -725,6 +725,27 @@ can be set to use the older authentication with a command such as
 
 .. seealso:: <https://github.com/phpmyadmin/phpmyadmin/issues/14220>, <https://stackoverflow.com/questions/49948350/phpmyadmin-on-mysql-8-0>, <https://bugs.php.net/bug.php?id=76243>
 
+.. _faq1_46:
+
+1.46 Missing ``HTTP_HOST`` variable when using nginx with HTTP/3
+-----------------------------------------------------------------------------------------------------------
+
+When using phpMyAdmin with nginx and HTTP/3 enabled, the ``HTTP_HOST`` variable may be missing due to a known issue with nginx's HTTP/3 implementation, which can cause several issues:
+
+- Two-factor authentication won't work
+- Exported settings have no hostname in the filename (e.g., ``phpMyAdmin-config-.json``)
+- The hostname is missing from the page title (empty ``@HTTP_HOST@``)
+
+To fix this issue, add the following line to your nginx configuration:
+
+.. code-block:: nginx
+
+    fastcgi_param HTTP_HOST $host;
+
+This line should be placed in the server block of your nginx configuration where the PHP-FPM settings are defined.
+
+.. seealso:: <https://github.com/php/php-src/issues/13021>, <https://github.com/nginx/nginx/issues/455>, <https://trac.nginx.org/nginx/ticket/2281>, <https://mailman.nginx.org/pipermail/nginx-devel/2024-January/3CQEHII5QU2BTQ7L7DAVCBWK3OQS3GU6.html>
+
 .. _faqconfig:
 
 Configuration
diff --git a/libraries/classes/Controllers/HomeController.php b/libraries/classes/Controllers/HomeController.php
index c4b929f970..d3c0f6c58e 100644
--- a/libraries/classes/Controllers/HomeController.php
+++ b/libraries/classes/Controllers/HomeController.php
@@ -8,6 +8,7 @@ use PhpMyAdmin\Charsets;
 use PhpMyAdmin\CheckUserPrivileges;
 use PhpMyAdmin\Config;
 use PhpMyAdmin\ConfigStorage\Relation;
+use PhpMyAdmin\Core;
 use PhpMyAdmin\DatabaseInterface;
 use PhpMyAdmin\Git;
 use PhpMyAdmin\Html\Generator;
@@ -398,6 +399,21 @@ class HomeController extends AbstractController
             ];
         }
 
+        /**
+         * Check for missing HTTP_HOST
+         * This commonly occurs with nginx >= 1.25.0 and HTTP/3 configurations
+         */
+        if (Core::getenv('HTTP_HOST') === '') {
+            $this->errors[] = [
+                'message' => __(
+                    'The [code]HTTP_HOST[/code] variable is missing,'
+                    . ' which might cause phpMyAdmin to not work properly.'
+                    . ' Please refer to [doc@faq1-46]documentation[/doc] for possible issues.',
+                ),
+                'severity' => 'warning',
+            ];
+        }
+
         $this->checkLanguageStats();
     }