# UNDF: UNDF-2026-000001121
# UNDF: UNDF-2026-XXXXXXXXX
--- a/src/network/room.cpp
+++ b/src/network/room.cpp
@@ -1,8 +1,8 @@
 // Copyright Citra Emulator Project / Azahar Emulator Project
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.

-#include <algorithm>
 #include <atomic>
 #include <mutex>
 #include <random>
 #include <regex>
 #include <sstream>
 #include <thread>
+#include <unordered_set>
 #include "common/logging/log.h"
 #include "enet/enet.h"
 #include "network/packet.h"
@@ -48,8 +48,8 @@ class Room::RoomImpl {
 public:
     // ...
-    UsernameBanList username_ban_list; ///< List of banned usernames
-    IPBanList ip_ban_list;             ///< List of banned IP addresses
+    std::unordered_set<std::string> username_ban_list; ///< Set of banned usernames (O(1) lookup)
+    std::unordered_set<std::string> ip_ban_list;       ///< Set of banned IP addresses (O(1) lookup)
     mutable std::mutex ban_list_mutex; ///< Mutex for the ban lists

@@ -383,14 +383,10 @@ void Room::RoomImpl::HandleJoinRequest(const ENetEvent* event) {
     {
         std::lock_guard lock(ban_list_mutex);

         // Check username ban
         if (!member.user_data.username.empty() &&
-            std::find(username_ban_list.begin(), username_ban_list.end(),
-                      member.user_data.username) != username_ban_list.end()) {
+            username_ban_list.count(member.user_data.username) != 0) {
             SendUserBanned(event->peer);
             return;
         }

         // Check IP ban
         char ip_raw[256];
         enet_address_get_host_ip(&event->peer->address, ip_raw, sizeof(ip_raw) - 1);
         ip = ip_raw;

-        if (std::find(ip_ban_list.begin(), ip_ban_list.end(), ip) != ip_ban_list.end()) {
+        if (ip_ban_list.count(ip) != 0) {
             SendUserBanned(event->peer);
             return;
         }
     }

@@ -503,15 +499,10 @@ void Room::RoomImpl::HandleModBanPacket(const ENetEvent* event) {
         if (!username.empty()) {
             // Ban the forum username
-            if (std::find(username_ban_list.begin(), username_ban_list.end(), username) ==
-                username_ban_list.end()) {
-                username_ban_list.emplace_back(username);
-            }
+            username_ban_list.insert(username);
         }

         // Ban the member's IP as well
-        if (std::find(ip_ban_list.begin(), ip_ban_list.end(), ip) == ip_ban_list.end()) {
-            ip_ban_list.emplace_back(ip);
-        }
+        ip_ban_list.insert(ip);
     }

@@ -535,14 +526,10 @@ void Room::RoomImpl::HandleModUnbanPacket(const ENetEvent* event) {
     bool unbanned = false;
     {
         std::lock_guard lock(ban_list_mutex);

-        auto it = std::find(username_ban_list.begin(), username_ban_list.end(), address);
-        if (it != username_ban_list.end()) {
+        if (username_ban_list.erase(address) > 0) {
             unbanned = true;
-            username_ban_list.erase(it);
         }

-        it = std::find(ip_ban_list.begin(), ip_ban_list.end(), address);
-        if (it != ip_ban_list.end()) {
+        if (ip_ban_list.erase(address) > 0) {
             unbanned = true;
-            ip_ban_list.erase(it);
         }
     }

@@ -739,8 +726,10 @@ void Room::RoomImpl::SendModBanListResponse(ENetPeer* client) {
     Packet packet;
     packet << static_cast<u8>(IdModBanListResponse);
     {
         std::lock_guard lock(ban_list_mutex);
-        packet << username_ban_list;
-        packet << ip_ban_list;
+        std::vector<std::string> unames(username_ban_list.begin(), username_ban_list.end());
+        std::vector<std::string> ips(ip_ban_list.begin(), ip_ban_list.end());
+        packet << unames;
+        packet << ips;
     }
     ENetPacket* enet_packet =
         enet_packet_create(packet.GetData(), packet.GetDataSize(), ENET_PACKET_FLAG_RELIABLE);

@@ -1043,8 +1032,10 @@ bool Room::Create(const std::string& name, const std::string& description,
     room_impl->password = password;
     room_impl->verify_backend = std::move(verify_backend);
-    room_impl->username_ban_list = ban_list.first;
-    room_impl->ip_ban_list = ban_list.second;
+    room_impl->username_ban_list =
+        std::unordered_set<std::string>(ban_list.first.begin(), ban_list.first.end());
+    room_impl->ip_ban_list =
+        std::unordered_set<std::string>(ban_list.second.begin(), ban_list.second.end());
     room_impl->StartLoop();
     return true;

@@ -1065,7 +1056,9 @@ Room::BanList Room::GetBanList() const {
     std::lock_guard lock(room_impl->ban_list_mutex);
-    return {room_impl->username_ban_list, room_impl->ip_ban_list};
+    return {
+        UsernameBanList(room_impl->username_ban_list.begin(), room_impl->username_ban_list.end()),
+        IPBanList(room_impl->ip_ban_list.begin(), room_impl->ip_ban_list.end()),
+    };
 }