diff --git a/src/load_okt.cpp b/src/load_okt.cpp
index 764ae320..21bf6db0 100644
--- a/src/load_okt.cpp
+++ b/src/load_okt.cpp
@@ -13,18 +13,20 @@
 
 //#pragma warning(disable:4244)
 
+#define MAGIC(a,b,c,d) (((a) << 24UL) | ((b) << 16UL) | ((c) << 8UL) | (d))
+
+#pragma pack(1)
 typedef struct OKTFILEHEADER
 {
 	DWORD okta;		// "OKTA"
 	DWORD song;		// "SONG"
 	DWORD cmod;		// "CMOD"
-	DWORD fixed8;
+	DWORD cmodlen;
 	BYTE chnsetup[8];
 	DWORD samp;		// "SAMP"
 	DWORD samplen;
 } OKTFILEHEADER;
 
-
 typedef struct OKTSAMPLE
 {
 	CHAR name[20];
@@ -36,20 +38,29 @@ typedef struct OKTSAMPLE
 	BYTE pad2;
 	BYTE pad3;
 } OKTSAMPLE;
+#pragma pack()
+
 
+static DWORD readBE32(const BYTE *v)
+{
+	return (v[0] << 24UL) | (v[1] << 16UL) | (v[2] << 8UL) | v[3];
+}
 
 BOOL CSoundFile::ReadOKT(const BYTE *lpStream, DWORD dwMemLength)
 //---------------------------------------------------------------
 {
 	const OKTFILEHEADER *pfh = (OKTFILEHEADER *)lpStream;
-	DWORD dwMemPos = sizeof(OKTFILEHEADER);
+	DWORD dwMemPos = sizeof(OKTFILEHEADER), dwSize;
 	UINT nsamples = 0, npatterns = 0, norders = 0;
 
 	if ((!lpStream) || (dwMemLength < 1024)) return FALSE;
-	if ((pfh->okta != 0x41544B4F) || (pfh->song != 0x474E4F53)
-	 || (pfh->cmod != 0x444F4D43) || (pfh->chnsetup[0]) || (pfh->chnsetup[2])
-	 || (pfh->chnsetup[4]) || (pfh->chnsetup[6]) || (pfh->fixed8 != 0x08000000)
-	 || (pfh->samp != 0x504D4153)) return FALSE;
+	if ((bswapBE32(pfh->okta) != MAGIC('O','K','T','A'))
+	 || (bswapBE32(pfh->song) != MAGIC('S','O','N','G'))
+	 || (bswapBE32(pfh->cmod) != MAGIC('C','M','O','D'))
+	 || (bswapBE32(pfh->cmodlen) != 8)
+	 || (pfh->chnsetup[0]) || (pfh->chnsetup[2])
+	 || (pfh->chnsetup[4]) || (pfh->chnsetup[6])
+	 || (bswapBE32(pfh->samp) != MAGIC('S','A','M','P'))) return FALSE;
 	m_nType = MOD_TYPE_OKT;
 	m_nChannels = 4 + pfh->chnsetup[1] + pfh->chnsetup[3] + pfh->chnsetup[5] + pfh->chnsetup[7];
 	if (m_nChannels > MAX_CHANNELS) m_nChannels = MAX_CHANNELS;
@@ -62,7 +73,7 @@ BOOL CSoundFile::ReadOKT(const BYTE *lpStream, DWORD dwMemLength)
 		if (dwMemPos >= dwMemLength - sizeof(OKTSAMPLE)) return TRUE;
 		if (smp < MAX_SAMPLES)
 		{
-			OKTSAMPLE *psmp = (OKTSAMPLE *)(lpStream + dwMemPos);
+			const OKTSAMPLE *psmp = (const OKTSAMPLE *)(lpStream + dwMemPos);
 			MODINSTRUMENT *pins = &Ins[smp];
 
 			memcpy(m_szNames[smp], psmp->name, 20);
@@ -79,41 +90,51 @@ BOOL CSoundFile::ReadOKT(const BYTE *lpStream, DWORD dwMemLength)
 	}
 	// SPEE
 	if (dwMemPos >= dwMemLength - 12) return TRUE;
-	if (*((DWORD *)(lpStream + dwMemPos)) == 0x45455053)
+	if (readBE32(lpStream + dwMemPos) == MAGIC('S','P','E','E'))
 	{
 		m_nDefaultSpeed = lpStream[dwMemPos+9];
-		dwMemPos += bswapBE32(*((DWORD *)(lpStream + dwMemPos + 4))) + 8;
+
+		dwSize = readBE32(lpStream + dwMemPos + 4);
+		if (dwSize > dwMemLength - 8 || dwMemPos > dwMemLength - dwSize - 8) return TRUE;
+		dwMemPos += dwSize + 8;
 	}
 	// SLEN
 	if (dwMemPos + 10 > dwMemLength) return TRUE;
-	if (*((DWORD *)(lpStream + dwMemPos)) == 0x4E454C53)
+	if (readBE32(lpStream + dwMemPos) == MAGIC('S','L','E','N'))
 	{
-		if (dwMemPos + 10 > dwMemLength) return TRUE;
 		npatterns = lpStream[dwMemPos+9];
-		dwMemPos += bswapBE32(*((DWORD *)(lpStream + dwMemPos + 4))) + 8;
+
+		dwSize = readBE32(lpStream + dwMemPos + 4);
+		if (dwSize > dwMemLength - 8 || dwMemPos > dwMemLength - dwSize - 8) return TRUE;
+		dwMemPos += dwSize + 8;
 	}
 	// PLEN
 	if (dwMemPos + 10 > dwMemLength) return TRUE;
-	if (*((DWORD *)(lpStream + dwMemPos)) == 0x4E454C50)
+	if (readBE32(lpStream + dwMemPos) == MAGIC('P','L','E','N'))
 	{
-		if (dwMemPos + 10 > dwMemLength) return TRUE;
 		norders = lpStream[dwMemPos+9];
-		dwMemPos += bswapBE32(*((DWORD *)(lpStream + dwMemPos + 4))) + 8;
+
+		dwSize = readBE32(lpStream + dwMemPos + 4);
+		if (dwSize > dwMemLength - 8 || dwMemPos > dwMemLength - dwSize - 8) return TRUE;
+		dwMemPos += dwSize + 8;
 	}
 	// PATT
 	if (dwMemPos + 8 > dwMemLength) return TRUE;
-	if (*((DWORD *)(lpStream + dwMemPos)) == 0x54544150)
+	if (readBE32(lpStream + dwMemPos) == MAGIC('P','A','T','T'))
 	{
 		UINT orderlen = norders;
 		if (orderlen >= MAX_ORDERS) orderlen = MAX_ORDERS-1;
 		if (dwMemPos + 8 + orderlen > dwMemLength) return TRUE;
 		for (UINT i=0; i<orderlen; i++) Order[i] = lpStream[dwMemPos+8+i];
 		for (UINT j=orderlen; j>1; j--) { if (Order[j-1]) break; Order[j-1] = 0xFF; }
-		dwMemPos += bswapBE32(*((DWORD *)(lpStream + dwMemPos + 4))) + 8;
+
+		dwSize = readBE32(lpStream + dwMemPos + 4);
+		if (dwSize > dwMemLength - 8 || dwMemPos > dwMemLength - dwSize - 8) return TRUE;
+		dwMemPos += dwSize + 8;
 	}
 	// PBOD
 	UINT npat = 0;
-	while ((dwMemPos < dwMemLength - 10) && (*((DWORD *)(lpStream + dwMemPos)) == 0x444F4250))
+	while ((dwMemPos < dwMemLength - 10) && (readBE32(lpStream + dwMemPos) == MAGIC('P','B','O','D')))
 	{
 		DWORD dwPos = dwMemPos + 10;
 		UINT rows = lpStream[dwMemPos+9];
@@ -185,15 +206,21 @@ BOOL CSoundFile::ReadOKT(const BYTE *lpStream, DWORD dwMemLength)
 			}
 		}
 		npat++;
-		dwMemPos += bswapBE32(*((DWORD *)(lpStream + dwMemPos + 4))) + 8;
+
+		dwSize = readBE32(lpStream + dwMemPos + 4);
+		if (dwSize > dwMemLength - 8 || dwMemPos > dwMemLength - dwSize - 8) return TRUE;
+		dwMemPos += dwSize + 8;
 	}
 	// SBOD
 	UINT nsmp = 1;
-	while ((dwMemPos < dwMemLength-10) && (*((DWORD *)(lpStream + dwMemPos)) == 0x444F4253))
+	while ((dwMemPos < dwMemLength-10) && (readBE32(lpStream + dwMemPos) == MAGIC('S','B','O','D')))
 	{
 		if (nsmp < MAX_SAMPLES) ReadSample(&Ins[nsmp], RS_PCM8S, (LPSTR)(lpStream+dwMemPos+8), dwMemLength-dwMemPos-8);
-		dwMemPos += bswapBE32(*((DWORD *)(lpStream + dwMemPos + 4))) + 8;
 		nsmp++;
+
+		dwSize = readBE32(lpStream + dwMemPos + 4);
+		if (dwSize > dwMemLength - 8 || dwMemPos > dwMemLength - dwSize - 8) return TRUE;
+		dwMemPos += dwSize + 8;
 	}
 	return TRUE;
 }
diff --git a/src/load_s3m.cpp b/src/load_s3m.cpp
index adcfb1f7..56f8f325 100644
--- a/src/load_s3m.cpp
+++ b/src/load_s3m.cpp
@@ -282,8 +282,6 @@ BOOL CSoundFile::ReadS3M(const BYTE *lpStream, DWORD dwMemLength)
 		}
 		if (psfh.panning_present == 252)
 		{
-			if (dwMemPos + 32 > dwMemLength) return FALSE;
-
 			const BYTE *chnpan = lpStream+dwMemPos;
 			if (dwMemPos > dwMemLength - 32) return FALSE;
 			for (UINT i=0; i<32; i++) if (chnpan[i] & 0x20)
diff --git a/src/load_ult.cpp b/src/load_ult.cpp
index eddc9a43..91a732b9 100644
--- a/src/load_ult.cpp
+++ b/src/load_ult.cpp
@@ -155,16 +155,15 @@ BOOL CSoundFile::ReadUlt(const BYTE *lpStream, DWORD dwMemLength)
 			UINT row = 0;
 			while (row < 64)
 			{
-				if (dwMemPos + 5 > dwMemLength) return TRUE;
+				if (dwMemPos > dwMemLength - 5) return TRUE;
 				UINT rep = 1;
 				UINT note = lpStream[dwMemPos++];
 				if (note == 0xFC)
 				{
-					if (dwMemPos + 7 > dwMemLength) return TRUE;
 					rep = lpStream[dwMemPos];
 					note = lpStream[dwMemPos+1];
 					dwMemPos += 2;
-                    if (dwMemPos + 4 > dwMemLength) return TRUE;
+					if (dwMemPos > dwMemLength - 4) return TRUE;
 				}
 
 				UINT instr = lpStream[dwMemPos++];