diff --git a/src/network/protocols/server_lobby.cpp b/src/network/protocols/server_lobby.cpp
index 50f7befde6a..5d854bfec5e 100644
--- a/src/network/protocols/server_lobby.cpp
+++ b/src/network/protocols/server_lobby.cpp
@@ -1247,7 +1247,13 @@ void ServerLobby::liveJoinRequest(Event* event)
     if (!spectator)
     {
         auto spectators_by_limit = getSpectatorsByLimit();
-        setPlayerKarts(data, peer);
+        if (!setPlayerKarts(data, peer))
+        {
+            // The kart list is part of the live-join request. Do not continue
+            // with uninitialised kart data after rejecting a malformed list.
+            rejectLiveJoin(peer, BLR_NONE);
+            return;
+        }
 
         std::vector<int> used_id;
         for (unsigned i = 0; i < peer->getPlayerProfiles().size(); i++)
@@ -4167,9 +4173,15 @@ void ServerLobby::addLiveJoinPlaceholder(
 }   // addLiveJoinPlaceholder
 
 //-----------------------------------------------------------------------------
-void ServerLobby::setPlayerKarts(const NetworkString& ns, STKPeer* peer) const
+bool ServerLobby::setPlayerKarts(const NetworkString& ns, STKPeer* peer) const
 {
     unsigned player_count = ns.getUInt8();
+    if (player_count > peer->getPlayerProfiles().size())
+    {
+        Log::warn("ServerLobby", "Too many kart entries from %s.",
+            peer->getAddress().toString().c_str());
+        return false;
+    }
     for (unsigned i = 0; i < player_count; i++)
     {
         std::string kart;
@@ -4192,7 +4204,7 @@ void ServerLobby::setPlayerKarts(const NetworkString& ns, STKPeer* peer) const
     }
     if (peer->getClientCapabilities().find("real_addon_karts") ==
         peer->getClientCapabilities().end() || ns.size() == 0)
-        return;
+        return true;
     for (unsigned i = 0; i < player_count; i++)
     {
         KartData kart_data(ns);
@@ -4219,6 +4231,7 @@ void ServerLobby::setPlayerKarts(const NetworkString& ns, STKPeer* peer) const
             player->setKartData(kart_data);
         }
     }
+    return true;
 }   // setPlayerKarts
 
 //-----------------------------------------------------------------------------
diff --git a/src/network/protocols/server_lobby.hpp b/src/network/protocols/server_lobby.hpp
index bbb6ed8ad59..f838fb0f56c 100644
--- a/src/network/protocols/server_lobby.hpp
+++ b/src/network/protocols/server_lobby.hpp
@@ -270,7 +270,7 @@ class ServerLobby : public LobbyProtocol
     void encodePlayers(BareNetworkString* bns,
         std::vector<std::shared_ptr<NetworkPlayerProfile> >& players) const;
     std::vector<std::shared_ptr<NetworkPlayerProfile> > getLivePlayers() const;
-    void setPlayerKarts(const NetworkString& ns, STKPeer* peer) const;
+    bool setPlayerKarts(const NetworkString& ns, STKPeer* peer) const;
     bool handleAssets(const NetworkString& ns, STKPeer* peer);
     void liveJoinRequest(Event* event);
     void rejectLiveJoin(STKPeer* peer, BackLobbyReason blr);