diff --git a/distribution/changelog.txt b/distribution/changelog.txt
index c530f1c585..c13c959ac3 100644
--- a/distribution/changelog.txt
+++ b/distribution/changelog.txt
@@ -14,6 +14,7 @@
 - Fix: [#20737] Spent money in player window underflows when getting refunds.
 - Fix: [#20778] [Plugin] Incorrect target api when executing custom actions.
 - Fix: [#20807] Tertiary colour not copied with small scenery.
+- Fix: [#20964] Crash when player connects to server with a group assigned that no longer exists.
 
 0.4.6 (2023-09-03)
 ------------------------------------------------------------------------
diff --git a/src/openrct2/network/NetworkBase.cpp b/src/openrct2/network/NetworkBase.cpp
index 2567717efe..46cbcc42ab 100644
--- a/src/openrct2/network/NetworkBase.cpp
+++ b/src/openrct2/network/NetworkBase.cpp
@@ -2643,7 +2643,10 @@ void NetworkBase::ServerHandleAuth(NetworkConnection& connection, NetworkPacket&
         if (connection.AuthStatus == NetworkAuth::Verified)
         {
             const NetworkGroup* group = GetGroupByID(GetGroupIDByHash(connection.Key.PublicKeyHash()));
-            passwordless = group->CanPerformAction(NetworkPermission::PasswordlessLogin);
+            if (group != nullptr)
+            {
+                passwordless = group->CanPerformAction(NetworkPermission::PasswordlessLogin);
+            }
         }
         if (gameversion != NetworkGetVersion())
         {
@@ -3649,6 +3652,11 @@ GameActions::Result NetworkModifyGroups(
         case ModifyGroupType::SetName:
         {
             NetworkGroup* group = network.GetGroupByID(groupId);
+            if (group == nullptr)
+            {
+                return GameActions::Result(GameActions::Status::InvalidParameters, STR_CANT_RENAME_GROUP, STR_NONE);
+            }
+
             const char* oldName = group->GetName().c_str();
 
             if (strcmp(oldName, name.c_str()) == 0)