diff --git a/protocol/build.gradle.kts b/protocol/build.gradle.kts
index 04c81b01..1b0949d7 100644
--- a/protocol/build.gradle.kts
+++ b/protocol/build.gradle.kts
@@ -9,6 +9,7 @@ dependencies {
     api(libs.netty.codec.core)
 
     implementation(projects.buffer)
+    implementation(projects.util)
 }
 
 publishing {
diff --git a/protocol/src/main/kotlin/org/openrs2/protocol/ProtocolModule.kt b/protocol/src/main/kotlin/org/openrs2/protocol/ProtocolModule.kt
index 8af99593..8417994b 100644
--- a/protocol/src/main/kotlin/org/openrs2/protocol/ProtocolModule.kt
+++ b/protocol/src/main/kotlin/org/openrs2/protocol/ProtocolModule.kt
@@ -12,6 +12,7 @@ import org.openrs2.protocol.login.downstream.IpLimitCodec
 import org.openrs2.protocol.login.downstream.Js5OkCodec
 import org.openrs2.protocol.login.downstream.LoginDownstream
 import org.openrs2.protocol.login.downstream.ServerFullCodec
+import org.openrs2.protocol.login.upstream.CheckWorldSuitabilityCodec
 import org.openrs2.protocol.login.upstream.InitCrossDomainConnectionCodec
 import org.openrs2.protocol.login.upstream.InitGameConnectionCodec
 import org.openrs2.protocol.login.upstream.InitJaggrabConnectionCodec
@@ -32,6 +33,7 @@ public object ProtocolModule : AbstractModule() {
             InitJs5RemoteConnectionCodec::class.java,
             InitJaggrabConnectionCodec::class.java,
             RequestWorldListCodec::class.java,
+            CheckWorldSuitabilityCodec::class.java,
             InitCrossDomainConnectionCodec::class.java
         )
 
diff --git a/protocol/src/main/kotlin/org/openrs2/protocol/login/upstream/CheckWorldSuitabilityCodec.kt b/protocol/src/main/kotlin/org/openrs2/protocol/login/upstream/CheckWorldSuitabilityCodec.kt
new file mode 100644
index 00000000..dcc353ef
--- /dev/null
+++ b/protocol/src/main/kotlin/org/openrs2/protocol/login/upstream/CheckWorldSuitabilityCodec.kt
@@ -0,0 +1,67 @@
+package org.openrs2.protocol.login.upstream
+
+import io.netty.buffer.ByteBuf
+import org.bouncycastle.crypto.params.RSAPrivateCrtKeyParameters
+import org.openrs2.buffer.readString
+import org.openrs2.buffer.use
+import org.openrs2.buffer.writeString
+import org.openrs2.crypto.Rsa
+import org.openrs2.crypto.StreamCipher
+import org.openrs2.crypto.rsa
+import org.openrs2.crypto.secureRandom
+import org.openrs2.protocol.PacketCodec
+import org.openrs2.protocol.PacketLength
+import org.openrs2.util.Base37
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+public class CheckWorldSuitabilityCodec @Inject constructor(
+    private val key: RSAPrivateCrtKeyParameters
+) : PacketCodec<LoginRequest.CheckWorldSuitability>(
+    type = LoginRequest.CheckWorldSuitability::class.java,
+    opcode = 24,
+    length = PacketLength.VARIABLE_BYTE
+) {
+    override fun decode(input: ByteBuf, cipher: StreamCipher): LoginRequest.CheckWorldSuitability {
+        val build = input.readShort().toInt()
+
+        val ciphertextLen = input.readUnsignedByte().toInt()
+        val ciphertext = input.readSlice(ciphertextLen)
+
+        ciphertext.rsa(key).use { plaintext ->
+            require(plaintext.readUnsignedByte().toInt() == Rsa.MAGIC) {
+                "Invalid RSA magic"
+            }
+            plaintext.skipBytes(4)
+
+            val username = Base37.decodeLowerCase(plaintext.readLong())
+            plaintext.skipBytes(4)
+
+            val password = plaintext.readString()
+            plaintext.skipBytes(4)
+
+            return LoginRequest.CheckWorldSuitability(build, username, password)
+        }
+    }
+
+    override fun encode(input: LoginRequest.CheckWorldSuitability, output: ByteBuf, cipher: StreamCipher) {
+        output.writeShort(input.build)
+
+        output.alloc().buffer().use { plaintext ->
+            plaintext.writeByte(Rsa.MAGIC)
+            plaintext.writeInt(secureRandom.nextInt())
+
+            plaintext.writeLong(Base37.encode(input.username))
+            plaintext.writeInt(secureRandom.nextInt())
+
+            plaintext.writeString(input.password)
+            plaintext.writeInt(secureRandom.nextInt())
+
+            plaintext.rsa(key).use { ciphertext ->
+                output.writeByte(ciphertext.readableBytes())
+                output.writeBytes(ciphertext)
+            }
+        }
+    }
+}
diff --git a/protocol/src/main/kotlin/org/openrs2/protocol/login/upstream/LoginRequest.kt b/protocol/src/main/kotlin/org/openrs2/protocol/login/upstream/LoginRequest.kt
index 577670e6..a83d7255 100644
--- a/protocol/src/main/kotlin/org/openrs2/protocol/login/upstream/LoginRequest.kt
+++ b/protocol/src/main/kotlin/org/openrs2/protocol/login/upstream/LoginRequest.kt
@@ -7,5 +7,10 @@ public sealed class LoginRequest : Packet {
     public data class InitJs5RemoteConnection(public val build: Int) : LoginRequest()
     public object InitJaggrabConnection : LoginRequest()
     public data class RequestWorldList(public val checksum: Int) : LoginRequest()
+    public data class CheckWorldSuitability(
+        public val build: Int,
+        public val username: String,
+        public val password: String
+    ) : LoginRequest()
     public object InitCrossDomainConnection : LoginRequest()
 }