diff --git a/providers/fab/src/airflow/providers/fab/auth_manager/security_manager/override.py b/providers/fab/src/airflow/providers/fab/auth_manager/security_manager/override.py
index 0cfc2351874a0..bd544cd0937c0 100644
--- a/providers/fab/src/airflow/providers/fab/auth_manager/security_manager/override.py
+++ b/providers/fab/src/airflow/providers/fab/auth_manager/security_manager/override.py
@@ -1495,8 +1495,9 @@ def update_user(self, user: User) -> bool:
                 new_group_ids = {grp.id for grp in user.groups}
                 if existing_role_ids != new_role_ids or existing_group_ids != new_group_ids:
                     user.changed_on = datetime.datetime.now(tz=datetime.timezone.utc)
-            self.session.merge(user)
+            merged_user = self.session.merge(user)
             self.session.commit()
+            self._reset_user_permissions_cache(merged_user)
             log.info(const.LOGMSG_INF_SEC_UPD_USER, user)
         except Exception as e:
             log.error(const.LOGMSG_ERR_SEC_UPD_USER, e)
@@ -1504,6 +1505,11 @@ def update_user(self, user: User) -> bool:
             return False
         return True
 
+    @staticmethod
+    def _reset_user_permissions_cache(user: User) -> None:
+        """Invalidate cached permissions to avoid stale auth checks after role updates."""
+        user._perms = None
+
     def del_register_user(self, register_user) -> bool:
         """
         Delete registration object from database.
@@ -1986,6 +1992,7 @@ def auth_user_ldap(self, username, password, rotate_session_id=True) -> User | N
             # Sync the user's roles
             if user and user_attributes and self.auth_roles_sync_at_login:
                 user.roles = self._ldap_calculate_user_roles(user_attributes)
+                self._reset_user_permissions_cache(user)
                 log.debug("Calculated new roles for user=%r as: %s", user_dn, user.roles)
 
             # If the user is new, register them
@@ -2013,6 +2020,8 @@ def auth_user_ldap(self, username, password, rotate_session_id=True) -> User | N
                 if rotate_session_id:
                     self._rotate_session_id()
                 self.update_user_auth_stat(user)
+                self.session.expire(user, ["roles", "groups"])
+                self._reset_user_permissions_cache(user)
                 return user
             return None
 
diff --git a/providers/fab/tests/unit/fab/auth_manager/security_manager/test_override.py b/providers/fab/tests/unit/fab/auth_manager/security_manager/test_override.py
index a2186c82973ba..409bd4bb700c9 100644
--- a/providers/fab/tests/unit/fab/auth_manager/security_manager/test_override.py
+++ b/providers/fab/tests/unit/fab/auth_manager/security_manager/test_override.py
@@ -26,9 +26,11 @@
 
 from airflow.providers.fab.auth_manager.models import (
     Action,
+    Group,
     Permission,
     Resource,
     Role,
+    User,
 )
 from airflow.providers.fab.auth_manager.security_manager.override import FabAirflowSecurityManagerOverride
 
@@ -193,6 +195,28 @@ def test_check_password_not_match(self, check_password):
         check_password.return_value = False
         assert not sm.check_password("test_user", "test_password")
 
+    def test_update_user_clears_cached_permissions(self):
+        sm = EmptySecurityManager()
+        user = Mock(
+            spec=User,
+            id=1,
+            roles=[Mock(spec=Role, id=2)],
+            groups=[Mock(spec=Group, id=3)],
+            _perms={("can_read", "DAG")},
+        )
+        existing_user = Mock(spec=User, roles=[Mock(spec=Role, id=4)], groups=[Mock(spec=Group, id=5)])
+        mock_merged_user = Mock(spec=User, _perms={("can_edit", "DAG")})
+        mock_session = Mock(spec=Session)
+        mock_session.get.return_value = existing_user
+        mock_session.merge.return_value = mock_merged_user
+
+        with mock.patch.object(EmptySecurityManager, "session", mock_session):
+            assert sm.update_user(user)
+
+        assert user._perms == {("can_read", "DAG")}
+        assert mock_merged_user._perms is None
+        mock_session.commit.assert_called_once_with()
+
     @pytest.mark.parametrize(
         ("provider", "resp", "user_info"),
         [