diff --git a/Core/HLE/sceMpeg.cpp b/Core/HLE/sceMpeg.cpp
index 2784f788b9..33b82f5a9b 100644
--- a/Core/HLE/sceMpeg.cpp
+++ b/Core/HLE/sceMpeg.cpp
@@ -962,6 +962,9 @@ static bool decodePmpVideo(PSPPointer<SceMpegRingBuffer> ringbuffer, u32 pmpctxA
 		// joint all blocks into H264Frames
 		for (int i = 0; i < pmp_nBlocks; i++){
 			auto lli = PSPPointer<SceMpegLLI>::Create(pmp_videoSource);
+			// Each block descriptor is in game memory, after the first.
+			if (!lli.IsValid())
+				break;
 			// add source block into pmpframes
 			const uint8_t *ptr = Memory::GetPointerRangeOrException(lli->pSrc, lli->iSize);
 			if (ptr)
diff --git a/Core/HLE/sceNetAdhoc.cpp b/Core/HLE/sceNetAdhoc.cpp
index 4ec5b5bc43..0cbcda4faa 100644
--- a/Core/HLE/sceNetAdhoc.cpp
+++ b/Core/HLE/sceNetAdhoc.cpp
@@ -3391,6 +3391,9 @@ int NetAdhocctl_CreateEnterGameMode(const char* group_name, int game_type, int n
 
 	if (game_type < ADHOCCTL_GAMETYPE_1A || game_type > ADHOCCTL_GAMETYPE_2A || num_members < 2 || num_members > 16 || (game_type == ADHOCCTL_GAMETYPE_1A && num_members > 4))
 		return SCE_NET_ADHOCCTL_ERROR_INVALID_ARG;
+	// The whole member list is read below.
+	if (!Memory::IsValidRange(membersAddr, num_members * (u32)sizeof(SceNetEtherAddr)))
+		return SCE_NET_ADHOCCTL_ERROR_INVALID_ARG;
 
 	// In a normal group, it reports ALREADY_CONNECTED through the handlers and stays in it
 	// (pspautotests net/adhoc/gamemode).
@@ -4615,7 +4618,8 @@ static int sceNetAdhocGameModeCreateMaster(MIPSState *mips, u32 dataAddr, int si
 	if (!netAdhocGameModeEntered)
 		return hleLogError(Log::sceNet, SCE_NET_ADHOCCTL_ERROR_NOT_ENTER_GAMEMODE, "not enter gamemode");
 
-	if (size < 0 || !Memory::IsValidAddress(dataAddr))
+	// The data is copied (and the buffers are sized) by size.
+	if (size < 0 || !Memory::IsValidAddress(dataAddr) || !Memory::IsValidRange(dataAddr, (u32)size))
 		return hleLogError(Log::sceNet, SCE_NET_ADHOCCTL_ERROR_INVALID_ARG, "invalid arg");
 
 	// pspautotests net/adhoc/pair/gamemode
@@ -4672,7 +4676,7 @@ static int sceNetAdhocGameModeCreateReplica(MIPSState *mips, const char *mac, u3
 	if (!netAdhocGameModeEntered)
 		return hleLogError(Log::sceNet, SCE_NET_ADHOCCTL_ERROR_NOT_ENTER_GAMEMODE, "not enter gamemode");
 
-	if (mac == nullptr || size < 0 || !Memory::IsValidAddress(dataAddr))
+	if (mac == nullptr || size < 0 || !Memory::IsValidAddress(dataAddr) || !Memory::IsValidRange(dataAddr, (u32)size))
 		return hleLogError(Log::sceNet, SCE_NET_ADHOCCTL_ERROR_INVALID_ARG, "invalid arg");
 
 	const SceNetEtherAddr &replicaMac = *(const SceNetEtherAddr *)mac;
diff --git a/Core/HLE/sceNetAdhocMatching.cpp b/Core/HLE/sceNetAdhocMatching.cpp
index fdce9166c2..687dc54dc1 100644
--- a/Core/HLE/sceNetAdhocMatching.cpp
+++ b/Core/HLE/sceNetAdhocMatching.cpp
@@ -1576,6 +1576,11 @@ static int sceNetAdhocMatchingCreate(MIPSState *mips, int mode, int maxnum, int
 		// Invalid Receive Buffer Size
 		return hleLogError(Log::sceNet, SCE_NET_ADHOC_MATCHING_ERROR_RXBUF_TOO_SHORT, "adhoc matching rxbuf too short");
 	}
+	// We allocate (and clear) this on the host. The PSP takes it from the library's small heap, and
+	// no packet is anywhere near this big.
+	if (rxbuflen > 1024 * 1024) {
+		return hleLogError(Log::sceNet, SCE_NET_ADHOC_MATCHING_ERROR_NO_SPACE, "adhoc matching rxbuf too large");
+	}
 
 	if (mode < 1 || mode > 3) {
 		return hleLogError(Log::sceNet, SCE_NET_ADHOC_MATCHING_ERROR_INVALID_MODE, "adhoc matching invalid mode");