diff --git a/vendor/magento/module-security/Model/AdminSessionInfo.php b/vendor/magento/module-security/Model/AdminSessionInfo.php
index c14d399e98ca..b0347fdbc3ad 100644
--- a/vendor/magento/module-security/Model/AdminSessionInfo.php
+++ b/vendor/magento/module-security/Model/AdminSessionInfo.php
@@ -47,6 +47,7 @@ class AdminSessionInfo extends \Magento\Framework\Model\AbstractModel
     /**
      * All other open sessions were terminated
      * @since 100.1.0
+     * @var bool
      */
     protected $isOtherSessionsTerminated = false;
 
@@ -133,10 +134,10 @@ public function isSessionExpired()
         $currentTime = $this->dateTime->gmtTimestamp();
         $lastUpdatedTime = $this->getUpdatedAt();
         if (!is_numeric($lastUpdatedTime)) {
-            $lastUpdatedTime = strtotime($lastUpdatedTime);
+            $lastUpdatedTime = $lastUpdatedTime === null ? 0 : strtotime($lastUpdatedTime);
         }
 
-        return $lastUpdatedTime <= ($currentTime - $lifetime) ? true : false;
+        return $lastUpdatedTime <= ($currentTime - $lifetime);
     }
 
     /**
diff --git a/vendor/magento/module-security/Model/AdminSessionsManager.php b/vendor/magento/module-security/Model/AdminSessionsManager.php
index 054bdd718432..6bab1694f9cf 100644
--- a/vendor/magento/module-security/Model/AdminSessionsManager.php
+++ b/vendor/magento/module-security/Model/AdminSessionsManager.php
@@ -7,8 +7,11 @@
 
 namespace Magento\Security\Model;
 
+use Magento\Backend\Model\Auth\Session;
 use Magento\Framework\HTTP\PhpEnvironment\RemoteAddress;
-use \Magento\Security\Model\ResourceModel\AdminSessionInfo\CollectionFactory;
+use Magento\Framework\Stdlib\DateTime;
+use Magento\Security\Model\ResourceModel\AdminSessionInfo\Collection;
+use Magento\Security\Model\ResourceModel\AdminSessionInfo\CollectionFactory;
 
 /**
  * Admin Sessions Manager Model
@@ -36,7 +39,7 @@ class AdminSessionsManager
     protected $securityConfig;
 
     /**
-     * @var \Magento\Backend\Model\Auth\Session
+     * @var Session
      * @since 100.1.0
      */
     protected $authSession;
@@ -74,12 +77,14 @@ class AdminSessionsManager
      *
      * Means that after session was prolonged
      * all other prolongs will be ignored within this period
+     *
+     * @var int
      */
     private $maxIntervalBetweenConsecutiveProlongs = 60;
 
     /**
      * @param ConfigInterface $securityConfig
-     * @param \Magento\Backend\Model\Auth\Session $authSession
+     * @param Session $authSession
      * @param AdminSessionInfoFactory $adminSessionInfoFactory
      * @param CollectionFactory $adminSessionInfoCollectionFactory
      * @param \Magento\Framework\Stdlib\DateTime\DateTime $dateTime
@@ -87,7 +92,7 @@ class AdminSessionsManager
      */
     public function __construct(
         ConfigInterface $securityConfig,
-        \Magento\Backend\Model\Auth\Session $authSession,
+        Session $authSession,
         \Magento\Security\Model\AdminSessionInfoFactory $adminSessionInfoFactory,
         \Magento\Security\Model\ResourceModel\AdminSessionInfo\CollectionFactory $adminSessionInfoCollectionFactory,
         \Magento\Framework\Stdlib\DateTime\DateTime $dateTime,
@@ -139,7 +144,7 @@ public function processProlong()
             $this->getCurrentSession()->setData(
                 'updated_at',
                 date(
-                    \Magento\Framework\Stdlib\DateTime::DATETIME_PHP_FORMAT,
+                    DateTime::DATETIME_PHP_FORMAT,
                     $this->authSession->getUpdatedAt()
                 )
             );
@@ -198,7 +203,7 @@ public function getLogoutReasonMessageByStatus($statusCode)
             case AdminSessionInfo::LOGGED_OUT_BY_LOGIN:
                 $reasonMessage = __(
                     'Someone logged into this account from another device or browser.'
-                    .' Your current session is terminated.'
+                    . ' Your current session is terminated.'
                 );
                 break;
             case AdminSessionInfo::LOGGED_OUT_MANUALLY:
@@ -235,7 +240,7 @@ public function getLogoutReasonMessage()
     /**
      * Get sessions for current user
      *
-     * @return \Magento\Security\Model\ResourceModel\AdminSessionInfo\Collection
+     * @return Collection
      * @since 100.1.0
      */
     public function getSessionsForCurrentUser()
@@ -308,9 +313,9 @@ protected function createNewSession()
     }
 
     /**
-     * Creates admin session information collection
+     * Retrieve new instance of admin session info collection
      *
-     * @return \Magento\Security\Model\ResourceModel\AdminSessionInfo\Collection
+     * @return Collection
      *
      * @since 100.1.0
      */
@@ -329,12 +334,16 @@ protected function createAdminSessionInfoCollection()
      */
     private function lastProlongIsOldEnough()
     {
-        $lastProlongTimestamp = strtotime($this->getCurrentSession()->getUpdatedAt());
+        $lastUpdatedTime = $this->getCurrentSession()->getUpdatedAt();
+        if ($lastUpdatedTime === null || is_numeric($lastUpdatedTime)) {
+            $lastUpdatedTime = "now";
+        }
+        $lastProlongTimestamp = strtotime($lastUpdatedTime);
         $nowTimestamp = $this->authSession->getUpdatedAt();
 
         $diff = $nowTimestamp - $lastProlongTimestamp;
 
-        return (float) $diff > $this->getIntervalBetweenConsecutiveProlongs();
+        return (float)$diff > $this->getIntervalBetweenConsecutiveProlongs();
     }
 
     /**
@@ -348,7 +357,7 @@ private function lastProlongIsOldEnough()
      */
     private function getIntervalBetweenConsecutiveProlongs()
     {
-        return (float) max(
+        return (float)max(
             1,
             min(
                 4 * log((float)$this->securityConfig->getAdminSessionLifetime()),