From e97200a8841c1dfb17bb0614be06d62e9d08b901 Mon Sep 17 00:00:00 2001
From: Acts1631 <acts1631kjv@proton.me>
Date: Tue, 6 Oct 2026 21:18:48 -0400
Subject: [PATCH] Reject invalid RPCN message types

RPCN forwards MessageDetails from other users. The protobuf uint16
wrappers can carry 32-bit values, and narrowing them on the recipient
aborts RPCS3.

Validate both values before casting so malformed messages are
discarded.
---
 rpcs3/Emu/NP/rpcn_client.cpp | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/rpcs3/Emu/NP/rpcn_client.cpp b/rpcs3/Emu/NP/rpcn_client.cpp
index deb4c9a0b7..885b29f825 100644
--- a/rpcs3/Emu/NP/rpcn_client.cpp
+++ b/rpcs3/Emu/NP/rpcn_client.cpp
@@ -3249,10 +3249,19 @@ namespace rpcn
 			return;
 		}
 
+		const u32 main_type = pb_mdata->maintype().value();
+		const u32 sub_type = pb_mdata->subtype().value();
+
+		if (main_type > std::numeric_limits<u16>::max() || sub_type > std::numeric_limits<u16>::max())
+		{
+			rpcn_log.warning("Discarded message with invalid type! (main_type=%u, sub_type=%u)", main_type, sub_type);
+			return;
+		}
+
 		message_data mdata = {
 			.msgId = message_counter,
-			.mainType = ::narrow<u16>(pb_mdata->maintype().value()),
-			.subType = ::narrow<u16>(pb_mdata->subtype().value()),
+			.mainType = static_cast<u16>(main_type),
+			.subType = static_cast<u16>(sub_type),
 			.msgFeatures = pb_mdata->msgfeatures(),
 			.subject = pb_mdata->subject(),
 			.body = pb_mdata->body()};