diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index 7848ac4b195ac..6eea8812edd8a 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -8619,8 +8619,22 @@ function getremoteaddr($default='0.0.0.0') {
     }
     if (!($variablestoskip & GETREMOTEADDR_SKIP_HTTP_X_FORWARDED_FOR)) {
         if (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
-            $hdr = explode(",", $_SERVER['HTTP_X_FORWARDED_FOR']);
-            $address = cleanremoteaddr($hdr[0]);
+            $forwardedaddresses = explode(",", $_SERVER['HTTP_X_FORWARDED_FOR']);
+            $address = $forwardedaddresses[0];
+
+            if (substr_count($address, ":") > 1) {
+                // Remove port and brackets from IPv6.
+                if (preg_match("/\[(.*)\]:/", $address, $matches)) {
+                    $address = $matches[1];
+                }
+            } else {
+                // Remove port from IPv4.
+                if (substr_count($address, ":") == 1) {
+                    $address = explode(":", $address)[0];
+                }
+            }
+
+            $address = cleanremoteaddr($address);
             return $address ? $address : $default;
         }
     }
diff --git a/lib/tests/moodlelib_test.php b/lib/tests/moodlelib_test.php
index e5331234308ef..fe1d6d601137b 100644
--- a/lib/tests/moodlelib_test.php
+++ b/lib/tests/moodlelib_test.php
@@ -2780,4 +2780,49 @@ public function test_count_words() {
         $count = count_words('one…two ブルース … カンベッル');
         $this->assertEquals(4, $count);
     }
+    /**
+     * Tests the getremoteaddr() function.
+     */
+    public function test_getremoteaddr() {
+        $xforwardedfor = isset($_SERVER['HTTP_X_FORWARDED_FOR']) ? $_SERVER['HTTP_X_FORWARDED_FOR'] : null;
+
+        $_SERVER['HTTP_X_FORWARDED_FOR'] = '';
+        $noip = getremoteaddr('1.1.1.1');
+        $this->assertEquals('1.1.1.1', $noip);
+
+        $_SERVER['HTTP_X_FORWARDED_FOR'] = '';
+        $noip = getremoteaddr();
+        $this->assertEquals('0.0.0.0', $noip);
+
+        $_SERVER['HTTP_X_FORWARDED_FOR'] = '127.0.0.1';
+        $singleip = getremoteaddr();
+        $this->assertEquals('127.0.0.1', $singleip);
+
+        $_SERVER['HTTP_X_FORWARDED_FOR'] = '127.0.0.1,127.0.0.2';
+        $twoip = getremoteaddr();
+        $this->assertEquals('127.0.0.1', $twoip);
+
+        $_SERVER['HTTP_X_FORWARDED_FOR'] = '127.0.0.1,127.0.0.2, 127.0.0.3';
+        $threeip = getremoteaddr();
+        $this->assertEquals('127.0.0.1', $threeip);
+
+        $_SERVER['HTTP_X_FORWARDED_FOR'] = '127.0.0.1:65535,127.0.0.2';
+        $portip = getremoteaddr();
+        $this->assertEquals('127.0.0.1', $portip);
+
+        $_SERVER['HTTP_X_FORWARDED_FOR'] = '0:0:0:0:0:0:0:1,127.0.0.2';
+        $portip = getremoteaddr();
+        $this->assertEquals('0:0:0:0:0:0:0:1', $portip);
+
+        $_SERVER['HTTP_X_FORWARDED_FOR'] = '0::1,127.0.0.2';
+        $portip = getremoteaddr();
+        $this->assertEquals('0:0:0:0:0:0:0:1', $portip);
+
+        $_SERVER['HTTP_X_FORWARDED_FOR'] = '[0:0:0:0:0:0:0:1]:65535,127.0.0.2';
+        $portip = getremoteaddr();
+        $this->assertEquals('0:0:0:0:0:0:0:1', $portip);
+
+        $_SERVER['HTTP_X_FORWARDED_FOR'] = $xforwardedfor;
+
+    }
 }