diff --git a/GPU/Common/SoftwareTransformCommon.cpp b/GPU/Common/SoftwareTransformCommon.cpp
index d4814de2bc11..ddea1366087f 100644
--- a/GPU/Common/SoftwareTransformCommon.cpp
+++ b/GPU/Common/SoftwareTransformCommon.cpp
@@ -483,7 +483,7 @@ void SoftwareTransform::Transform(int prim, u32 vertType, const DecVtxFormat &de
 	}
 }
 
-void SoftwareTransform::BuildDrawingParams(int prim, int vertexCount, u32 vertType, u16 *&inds, int indsSize, int &numDecodedVerts, SoftwareTransformResult *result) {
+void SoftwareTransform::BuildDrawingParams(int prim, int vertexCount, u32 vertType, u16 *&inds, int indsSize, int &numDecodedVerts, int vertsSize, SoftwareTransformResult *result) {
 	TransformedVertex *transformed = params_.transformed;
 	TransformedVertex *transformedExpanded = params_.transformedExpanded;
 	bool throughmode = (vertType & GE_VTYPE_THROUGH_MASK) != 0;
@@ -496,7 +496,7 @@ void SoftwareTransform::BuildDrawingParams(int prim, int vertexCount, u32 vertTy
 	bool useBufferedRendering = fbman->UseBufferedRendering();
 
 	if (prim == GE_PRIM_RECTANGLES) {
-		if (!ExpandRectangles(vertexCount, numDecodedVerts, inds, indsSize, transformed, transformedExpanded, numTrans, throughmode, &result->pixelMapped)) {
+		if (!ExpandRectangles(vertexCount, numDecodedVerts, vertsSize, inds, indsSize, transformed, transformedExpanded, numTrans, throughmode, &result->pixelMapped)) {
 			result->drawIndexed = false;
 			result->drawNumTrans = 0;
 			result->pixelMapped = false;
@@ -520,7 +520,7 @@ void SoftwareTransform::BuildDrawingParams(int prim, int vertexCount, u32 vertTy
 		}
 	} else if (prim == GE_PRIM_POINTS) {
 		result->pixelMapped = false;
-		if (!ExpandPoints(vertexCount, numDecodedVerts, inds, indsSize, transformed, transformedExpanded, numTrans, throughmode)) {
+		if (!ExpandPoints(vertexCount, numDecodedVerts, vertsSize, inds, indsSize, transformed, transformedExpanded, numTrans, throughmode)) {
 			result->drawIndexed = false;
 			result->drawNumTrans = 0;
 			return;
@@ -529,7 +529,7 @@ void SoftwareTransform::BuildDrawingParams(int prim, int vertexCount, u32 vertTy
 		result->drawIndexed = true;
 	} else if (prim == GE_PRIM_LINES) {
 		result->pixelMapped = false;
-		if (!ExpandLines(vertexCount, numDecodedVerts, inds, indsSize, transformed, transformedExpanded, numTrans, throughmode)) {
+		if (!ExpandLines(vertexCount, numDecodedVerts, vertsSize, inds, indsSize, transformed, transformedExpanded, numTrans, throughmode)) {
 			result->drawIndexed = false;
 			result->drawNumTrans = 0;
 			return;
@@ -657,12 +657,16 @@ void SoftwareTransform::CalcCullParams(float &minZValue, float &maxZValue) {
 		std::swap(minZValue, maxZValue);
 }
 
-bool SoftwareTransform::ExpandRectangles(int vertexCount, int &numDecodedVerts, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode, bool *pixelMappedExactly) const {
+bool SoftwareTransform::ExpandRectangles(int vertexCount, int &numDecodedVerts, int vertsSize, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode, bool *pixelMappedExactly) const {
 	// Before we start, do a sanity check - does the output fit?
 	if ((vertexCount / 2) * 6 > indsSize) {
 		// Won't fit, kill the draw.
 		return false;
 	}
+	if ((vertexCount / 2) * 4 > vertsSize) {
+		// Won't fit, kill the draw.
+		return false;
+	}
 
 	// Rectangles always need 2 vertices, disregard the last one if there's an odd number.
 	vertexCount = vertexCount & ~1;
@@ -754,12 +758,15 @@ bool SoftwareTransform::ExpandRectangles(int vertexCount, int &numDecodedVerts,
 	return true;
 }
 
-bool SoftwareTransform::ExpandLines(int vertexCount, int &numDecodedVerts, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode) const {
+bool SoftwareTransform::ExpandLines(int vertexCount, int &numDecodedVerts, int vertsSize, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode) const {
 	// Before we start, do a sanity check - does the output fit?
 	if ((vertexCount / 2) * 6 > indsSize) {
 		// Won't fit, kill the draw.
 		return false;
 	}
+	if ((vertexCount / 2) * 4 > vertsSize) {
+		return false;
+	}
 
 	// Lines always need 2 vertices, disregard the last one if there's an odd number.
 	vertexCount = vertexCount & ~1;
@@ -885,12 +892,16 @@ bool SoftwareTransform::ExpandLines(int vertexCount, int &numDecodedVerts, u16 *
 	return true;
 }
 
-bool SoftwareTransform::ExpandPoints(int vertexCount, int &maxIndex, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode) const {
+bool SoftwareTransform::ExpandPoints(int vertexCount, int &maxIndex, int vertsSize, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode) const {
 	// Before we start, do a sanity check - does the output fit?
 	if (vertexCount * 6 > indsSize) {
 		// Won't fit, kill the draw.
 		return false;
 	}
+	if (vertexCount * 4 > vertsSize) {
+		// Won't fit, kill the draw.
+		return false;
+	}
 
 	numTrans = 0;
 	TransformedVertex *trans = &transformedExpanded[0];
diff --git a/GPU/Common/SoftwareTransformCommon.h b/GPU/Common/SoftwareTransformCommon.h
index be851a2c326d..c33eb9151a67 100644
--- a/GPU/Common/SoftwareTransformCommon.h
+++ b/GPU/Common/SoftwareTransformCommon.h
@@ -71,13 +71,13 @@ class SoftwareTransform {
 
 	// NOTE: The viewport must be up to date!
 	// indsSize is in indices, not bytes.
-	void BuildDrawingParams(int prim, int vertexCount, u32 vertType, u16 *&inds, int indsSize, int &numDecodedVerts, SoftwareTransformResult *result);
+	void BuildDrawingParams(int prim, int vertexCount, u32 vertType, u16 *&inds, int indsSize, int &numDecodedVerts, int vertsSize, SoftwareTransformResult *result);
 
 protected:
 	void CalcCullParams(float &minZValue, float &maxZValue);
-	bool ExpandRectangles(int vertexCount, int &numDecodedVerts, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode, bool *pixelMappedExactly) const;
-	bool ExpandLines(int vertexCount, int &numDecodedVerts, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode) const;
-	bool ExpandPoints(int vertexCount, int &numDecodedVerts, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode) const;
+	bool ExpandRectangles(int vertexCount, int &numDecodedVerts, int vertsSize, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode, bool *pixelMappedExactly) const;
+	bool ExpandLines(int vertexCount, int &numDecodedVerts, int vertsSize, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode) const;
+	bool ExpandPoints(int vertexCount, int &numDecodedVerts, int vertsSize, u16 *&inds, int indsSize, const TransformedVertex *transformed, TransformedVertex *transformedExpanded, int &numTrans, bool throughmode) const;
 
 	const SoftwareTransformParams &params_;
 	Lin::Matrix4x4 projMatrix_;
diff --git a/GPU/D3D11/DrawEngineD3D11.cpp b/GPU/D3D11/DrawEngineD3D11.cpp
index b0d53f388565..e1c588b76b4c 100644
--- a/GPU/D3D11/DrawEngineD3D11.cpp
+++ b/GPU/D3D11/DrawEngineD3D11.cpp
@@ -418,7 +418,7 @@ void DrawEngineD3D11::DoFlush() {
 		ApplyDrawState(prim);
 
 		if (result.action == SW_NOT_READY)
-			swTransform.BuildDrawingParams(prim, vertexCount, dec_->VertexType(), inds, RemainingIndices(inds), numDecodedVerts_, &result);
+			swTransform.BuildDrawingParams(prim, vertexCount, dec_->VertexType(), inds, RemainingIndices(inds), numDecodedVerts_, VERTEX_BUFFER_MAX, &result);
 		if (result.setSafeSize)
 			framebufferManager_->SetSafeSize(result.safeWidth, result.safeHeight);
 
diff --git a/GPU/Directx9/DrawEngineDX9.cpp b/GPU/Directx9/DrawEngineDX9.cpp
index 5f76d8e58968..6fe9b3dd07a2 100644
--- a/GPU/Directx9/DrawEngineDX9.cpp
+++ b/GPU/Directx9/DrawEngineDX9.cpp
@@ -374,7 +374,7 @@ void DrawEngineDX9::DoFlush() {
 		ApplyDrawState(prim);
 
 		if (result.action == SW_NOT_READY)
-			swTransform.BuildDrawingParams(prim, vertexCount, dec_->VertexType(), inds, RemainingIndices(inds), numDecodedVerts_, &result);
+			swTransform.BuildDrawingParams(prim, vertexCount, dec_->VertexType(), inds, RemainingIndices(inds), numDecodedVerts_, VERTEX_BUFFER_MAX, &result);
 		if (result.setSafeSize)
 			framebufferManager_->SetSafeSize(result.safeWidth, result.safeHeight);
 
diff --git a/GPU/GLES/DrawEngineGLES.cpp b/GPU/GLES/DrawEngineGLES.cpp
index a52f405e80bc..4445dd57c353 100644
--- a/GPU/GLES/DrawEngineGLES.cpp
+++ b/GPU/GLES/DrawEngineGLES.cpp
@@ -403,7 +403,7 @@ void DrawEngineGLES::DoFlush() {
 		ApplyDrawState(prim);
 
 		if (result.action == SW_NOT_READY)
-			swTransform.BuildDrawingParams(prim, vertexCount, dec_->VertexType(), inds, RemainingIndices(inds), numDecodedVerts_, &result);
+			swTransform.BuildDrawingParams(prim, vertexCount, dec_->VertexType(), inds, RemainingIndices(inds), numDecodedVerts_, VERTEX_BUFFER_MAX, &result);
 		if (result.setSafeSize)
 			framebufferManager_->SetSafeSize(result.safeWidth, result.safeHeight);
 
diff --git a/GPU/GPUCommonHW.cpp b/GPU/GPUCommonHW.cpp
index 2e20702f6b7e..a3c1a8a02d83 100644
--- a/GPU/GPUCommonHW.cpp
+++ b/GPU/GPUCommonHW.cpp
@@ -973,8 +973,9 @@ void GPUCommonHW::Execute_Prim(u32 op, u32 diff) {
 	u32 vertexType = gstate.vertType;
 	if ((vertexType & GE_VTYPE_IDX_MASK) != GE_VTYPE_IDX_NONE) {
 		u32 indexAddr = gstate_c.indexAddr;
-		if (!Memory::IsValidAddress(indexAddr)) {
-			ERROR_LOG(G3D, "Bad index address %08x!", indexAddr);
+		u32 indexSize = (vertexType & GE_VTYPE_IDX_MASK) >> GE_VTYPE_IDX_SHIFT;
+		if (!Memory::IsValidRange(indexAddr, count * indexSize)) {
+			ERROR_LOG(G3D, "Bad index address %08x (%d)!", indexAddr, count);
 			return;
 		}
 		inds = Memory::GetPointerUnchecked(indexAddr);
diff --git a/GPU/Vulkan/DrawEngineVulkan.cpp b/GPU/Vulkan/DrawEngineVulkan.cpp
index 1247e0145d81..130eeaedd203 100644
--- a/GPU/Vulkan/DrawEngineVulkan.cpp
+++ b/GPU/Vulkan/DrawEngineVulkan.cpp
@@ -431,7 +431,7 @@ void DrawEngineVulkan::DoFlush() {
 
 		if (result.action == SW_NOT_READY) {
 			// decIndex_ here is always equal to inds currently, but it may not be in the future.
-			swTransform.BuildDrawingParams(prim, vertexCount, dec_->VertexType(), inds, RemainingIndices(inds), numDecodedVerts_, &result);
+			swTransform.BuildDrawingParams(prim, vertexCount, dec_->VertexType(), inds, RemainingIndices(inds), numDecodedVerts_, VERTEX_BUFFER_MAX, &result);
 		}
 
 		if (result.setSafeSize)