diff --git a/client/include/interface/renderer.h b/client/include/interface/renderer.h
index 3435855e..11c73f7e 100644
--- a/client/include/interface/renderer.h
+++ b/client/include/interface/renderer.h
@@ -161,6 +161,51 @@ typedef enum LG_RendererCursor
 }
 LG_RendererCursor;
 
+/* Current producers reserve at most a 512x512 32-bpp cursor payload.
+ * Monochrome wire heights contain vertically stacked AND and XOR masks. */
+#define LG_CURSOR_MAX_WIDTH     512
+#define LG_CURSOR_MAX_HEIGHT    512
+#define LG_CURSOR_MAX_DATA_SIZE \
+  ((size_t)LG_CURSOR_MAX_WIDTH * LG_CURSOR_MAX_HEIGHT * 4U)
+
+static inline bool lg_rendererCursorValidate(LG_RendererCursor type,
+    int width, int height, int pitch, size_t * dataSize)
+{
+  if (width <= 0 || height <= 0 || pitch <= 0 ||
+      width > LG_CURSOR_MAX_WIDTH)
+    return false;
+
+  size_t rowBytes;
+  int decodedHeight;
+  switch (type)
+  {
+    case LG_CURSOR_COLOR:
+    case LG_CURSOR_MASKED_COLOR:
+      rowBytes      = (size_t)width * 4U;
+      decodedHeight = height;
+      break;
+
+    case LG_CURSOR_MONOCHROME:
+      if (height & 1)
+        return false;
+      rowBytes      = ((size_t)width + 7U) / 8U;
+      decodedHeight = height / 2;
+      break;
+
+    default:
+      return false;
+  }
+
+  if (decodedHeight <= 0 || decodedHeight > LG_CURSOR_MAX_HEIGHT ||
+      (size_t)pitch < rowBytes ||
+      (size_t)pitch > LG_CURSOR_MAX_DATA_SIZE / (size_t)height)
+    return false;
+
+  if (dataSize)
+    *dataSize = (size_t)height * (size_t)pitch;
+  return true;
+}
+
 typedef struct LG_Renderer LG_Renderer;
 
 typedef enum LG_RendererInteropType
diff --git a/client/renderers/EGL/cursor.c b/client/renderers/EGL/cursor.c
index 4577bd21..8669be3f 100644
--- a/client/renderers/EGL/cursor.c
+++ b/client/renderers/EGL/cursor.c
@@ -83,6 +83,9 @@ struct EGL_Cursor
   int               stride;
   uint8_t *         data;
   size_t            dataSize;
+  uint32_t *        normData;
+  uint32_t *        monoData;
+  size_t            decodedCapacity;
   bool              update;
 
   // cursor state
@@ -255,6 +258,8 @@ void egl_cursorFree(EGL_Cursor ** cursor)
   LG_LOCK_FREE((*cursor)->lock);
   if ((*cursor)->data)
     free((*cursor)->data);
+  free((*cursor)->normData);
+  free((*cursor)->monoData);
 
   cursorTexFree(&(*cursor)->norm);
   cursorTexFree(&(*cursor)->mono);
@@ -266,34 +271,72 @@ void egl_cursorFree(EGL_Cursor ** cursor)
   *cursor = NULL;
 }
 
+static bool cursorEnsureDecoded(EGL_Cursor * cursor, size_t pixels)
+{
+  if (pixels <= cursor->decodedCapacity)
+    return true;
+
+  const size_t size = pixels * sizeof(*cursor->normData);
+  uint32_t * normData = malloc(size);
+  uint32_t * monoData = malloc(size);
+  if (!normData || !monoData)
+  {
+    free(normData);
+    free(monoData);
+    DEBUG_ERROR("Failed to allocate cursor conversion buffers");
+    return false;
+  }
+
+  free(cursor->normData);
+  free(cursor->monoData);
+  cursor->normData        = normData;
+  cursor->monoData        = monoData;
+  cursor->decodedCapacity = pixels;
+  return true;
+}
+
 bool egl_cursorSetShape(EGL_Cursor * cursor, const LG_RendererCursor type,
     const int width, const int height, const int stride, const uint8_t * data)
 {
+  size_t size;
+  if (!data || !lg_rendererCursorValidate(
+        type, width, height, stride, &size))
+  {
+    DEBUG_ERROR("Invalid cursor shape geometry");
+    return false;
+  }
+
+  const int decodedHeight =
+    type == LG_CURSOR_MONOCHROME ? height / 2 : height;
+  const size_t pixels = (size_t)width * (size_t)decodedHeight;
+
   LG_LOCK(cursor->lock);
 
-  cursor->type   = type;
-  cursor->width  = width;
-  cursor->height = (type == LG_CURSOR_MONOCHROME ? height / 2 : height);
-  cursor->stride = stride;
+  if (!cursorEnsureDecoded(cursor, pixels))
+  {
+    LG_UNLOCK(cursor->lock);
+    return false;
+  }
 
-  const size_t size = height * stride;
   if (size > cursor->dataSize)
   {
-    if (cursor->data)
-      free(cursor->data);
-
-    cursor->data = malloc(size);
-    if (!cursor->data)
+    uint8_t * resized = realloc(cursor->data, size);
+    if (!resized)
     {
       DEBUG_ERROR("Failed to malloc buffer for cursor shape");
       LG_UNLOCK(cursor->lock);
       return false;
     }
 
+    cursor->data     = resized;
     cursor->dataSize = size;
   }
 
   memcpy(cursor->data, data, size);
+  cursor->type   = type;
+  cursor->width  = width;
+  cursor->height = decodedHeight;
+  cursor->stride = stride;
   cursor->update = true;
 
   LG_UNLOCK(cursor->lock);
@@ -367,67 +410,92 @@ struct CursorState egl_cursorRender(EGL_Cursor * cursor,
 
     if (updateShape)
     {
-      uint8_t * data = cursor->data;
+      const uint8_t * data = cursor->data;
       switch(cursor->type)
       {
       case LG_CURSOR_MASKED_COLOR:
       {
-        uint32_t xor[cursor->height][cursor->width];
         for(int y = 0; y < cursor->height; ++y)
+        {
+          const uint8_t * row = data + (size_t)cursor->stride * (size_t)y;
           for(int x = 0; x < cursor->width; ++x)
           {
-            uint32_t * src = (uint32_t *)(data + (cursor->stride * y) + x * 4);
-            const bool masked = (*src & 0xFF000000) != 0;
+            uint32_t src;
+            memcpy(&src, row + (size_t)x * sizeof(src), sizeof(src));
+            const size_t index =
+              (size_t)y * (size_t)cursor->width + (size_t)x;
+            const bool masked = (src & 0xFF000000) != 0;
             if (masked)
-              *src = xor[y][x] = *src & 0x00FFFFFF;
+              cursor->normData[index] = cursor->monoData[index] =
+                src & 0x00FFFFFF;
             else
             {
-              xor[y][x]  = 0xFF000000;
-              *src      |= 0xFF000000;
+              cursor->normData[index] = src | 0xFF000000;
+              cursor->monoData[index] = 0xFF000000;
             }
           }
+        }
 
         egl_textureSetup(cursor->mono.texture, EGL_PF_BGRA,
-            cursor->width, cursor->height, cursor->width, sizeof(xor[0]));
-        egl_textureUpdate(cursor->mono.texture, (uint8_t *)xor, true);
-      }
-      // fall through
-
-      case LG_CURSOR_COLOR:
-      {
+            cursor->width, cursor->height, cursor->width,
+            (size_t)cursor->width * sizeof(*cursor->monoData));
+        egl_textureUpdate(cursor->mono.texture,
+            (const uint8_t *)cursor->monoData, true);
         egl_textureSetup(cursor->norm.texture, EGL_PF_BGRA,
-            cursor->width, cursor->height, cursor->width, cursor->stride);
-        egl_textureUpdate(cursor->norm.texture, data, true);
+            cursor->width, cursor->height, cursor->width,
+            (size_t)cursor->width * sizeof(*cursor->normData));
+        egl_textureUpdate(cursor->norm.texture,
+            (const uint8_t *)cursor->normData, true);
         break;
       }
 
+      case LG_CURSOR_COLOR:
+        for(int y = 0; y < cursor->height; ++y)
+          memcpy(cursor->normData + (size_t)y * (size_t)cursor->width,
+              data + (size_t)y * (size_t)cursor->stride,
+              (size_t)cursor->width * sizeof(*cursor->normData));
+
+        egl_textureSetup(cursor->norm.texture, EGL_PF_BGRA,
+            cursor->width, cursor->height, cursor->width,
+            (size_t)cursor->width * sizeof(*cursor->normData));
+        egl_textureUpdate(cursor->norm.texture,
+            (const uint8_t *)cursor->normData, true);
+        break;
+
       case LG_CURSOR_MONOCHROME:
       {
-        uint32_t and[cursor->height][cursor->width];
-        uint32_t xor[cursor->height][cursor->width];
-
         for(int y = 0; y < cursor->height; ++y)
         {
+          const uint8_t * srcAnd =
+            data + (size_t)cursor->stride * (size_t)y;
+          const uint8_t * srcXor = data +
+            (size_t)cursor->stride * (size_t)(y + cursor->height);
           for(int x = 0; x < cursor->width; ++x)
           {
-            const uint8_t  * srcAnd  = data + (cursor->stride * y) + (x / 8);
-            const uint8_t  * srcXor  = srcAnd + cursor->stride * cursor->height;
             const uint8_t    mask    = 0x80 >> (x % 8);
-            const uint32_t   andMask = (*srcAnd & mask) ? 0xFFFFFFFF : 0xFF000000;
-            const uint32_t   xorMask = (*srcXor & mask) ? 0x00FFFFFF : 0x00000000;
+            const uint32_t   andMask =
+              (srcAnd[x / 8] & mask) ? 0xFFFFFFFF : 0xFF000000;
+            const uint32_t   xorMask =
+              (srcXor[x / 8] & mask) ? 0x00FFFFFF : 0x00000000;
+            const size_t index =
+              (size_t)y * (size_t)cursor->width + (size_t)x;
 
-            and[y][x] = andMask;
-            xor[y][x] = xorMask;
+            cursor->normData[index] = andMask;
+            cursor->monoData[index] = xorMask;
           }
         }
 
         // Monochrome cursors use AND/XOR mask textures - never convert to PQ
         egl_textureSetup(cursor->norm.texture, EGL_PF_BGRA,
-            cursor->width, cursor->height, cursor->width, sizeof(and[0]));
+            cursor->width, cursor->height, cursor->width,
+            (size_t)cursor->width * sizeof(*cursor->normData));
         egl_textureSetup(cursor->mono.texture, EGL_PF_BGRA,
-            cursor->width, cursor->height, cursor->width, sizeof(xor[0]));
-        egl_textureUpdate(cursor->norm.texture, (uint8_t *)and, true);
-        egl_textureUpdate(cursor->mono.texture, (uint8_t *)xor, true);
+            cursor->width, cursor->height, cursor->width,
+            (size_t)cursor->width * sizeof(*cursor->monoData));
+        egl_textureUpdate(cursor->norm.texture,
+            (const uint8_t *)cursor->normData, true);
+        egl_textureUpdate(cursor->mono.texture,
+            (const uint8_t *)cursor->monoData, true);
         break;
       }
       }
diff --git a/client/renderers/OpenGL/opengl.c b/client/renderers/OpenGL/opengl.c
index 21557b62..8eac8b70 100644
--- a/client/renderers/OpenGL/opengl.c
+++ b/client/renderers/OpenGL/opengl.c
@@ -157,6 +157,8 @@ struct Inst
   int               mousePitch;
   uint8_t *         mouseData;
   size_t            mouseDataSize;
+  uint32_t *        mouseRGBA;
+  size_t            mouseRGBACapacity;
 
   bool              mouseUpdate;
   bool              newShape;
@@ -269,6 +271,7 @@ void opengl_deinitialize(LG_Renderer * renderer)
 
   if (this->mouseData)
     free(this->mouseData);
+  free(this->mouseRGBA);
 
   free(this->swSurfaceBuffer);
 
@@ -352,29 +355,52 @@ bool opengl_onMouseShape(LG_Renderer * renderer, const LG_RendererCursor cursor,
 {
   struct Inst * this = UPCAST(struct Inst, renderer);
 
+  size_t size;
+  if (!data || !lg_rendererCursorValidate(
+        cursor, width, height, pitch, &size))
+  {
+    DEBUG_ERROR("Invalid cursor shape geometry");
+    return false;
+  }
+
+  const size_t pixels = (size_t)width * (size_t)height;
+
   LG_LOCK(this->mouseLock);
+
+  if (size > this->mouseDataSize)
+  {
+    uint8_t * resized = realloc(this->mouseData, size);
+    if (!resized)
+    {
+      DEBUG_ERROR("Failed to allocate cursor shape buffer");
+      LG_UNLOCK(this->mouseLock);
+      return false;
+    }
+
+    this->mouseData     = resized;
+    this->mouseDataSize = size;
+  }
+
+  if (pixels > this->mouseRGBACapacity)
+  {
+    uint32_t * resized = realloc(
+        this->mouseRGBA, pixels * sizeof(*this->mouseRGBA));
+    if (!resized)
+    {
+      DEBUG_ERROR("Failed to allocate cursor conversion buffer");
+      LG_UNLOCK(this->mouseLock);
+      return false;
+    }
+
+    this->mouseRGBA         = resized;
+    this->mouseRGBACapacity = pixels;
+  }
+
+  memcpy(this->mouseData, data, size);
   this->mouseCursor = cursor;
   this->mouseWidth  = width;
   this->mouseHeight = height;
   this->mousePitch  = pitch;
-
-  const size_t size = height * pitch;
-  if (size > this->mouseDataSize)
-  {
-    if (this->mouseData)
-      free(this->mouseData);
-
-    this->mouseData = malloc(size);
-    if (!this->mouseData)
-    {
-      DEBUG_ERROR("out of memory");
-      return false;
-    }
-
-    this->mouseDataSize = size;
-  }
-
-  memcpy(this->mouseData, data, size);
   this->newShape = true;
   LG_UNLOCK(this->mouseLock);
 
@@ -1105,27 +1131,41 @@ static void updateMouseShape(struct Inst * this)
   const int               height = this->mouseHeight;
   const int               pitch  = this->mousePitch;
   const uint8_t *         data   = this->mouseData;
-
-  // tmp buffer for masked colour
-  uint32_t tmp[width * height];
+  uint32_t              * rgba   = this->mouseRGBA;
 
   this->mouseType = cursor;
   switch(cursor)
   {
     case LG_CURSOR_MASKED_COLOR:
-      for(int i = 0; i < width * height; ++i)
+      for(int y = 0; y < height; ++y)
       {
-        const uint32_t c = ((uint32_t *)data)[i];
-        tmp[i] = (c & ~0xFF000000) | (c & 0xFF000000 ? 0x0 : 0xFF000000);
+        const uint8_t * row = data + (size_t)pitch * (size_t)y;
+        for(int x = 0; x < width; ++x)
+        {
+          uint32_t c;
+          memcpy(&c, row + (size_t)x * sizeof(c), sizeof(c));
+          rgba[(size_t)y * (size_t)width + (size_t)x] =
+            (c & ~0xFF000000) |
+            (c & 0xFF000000 ? 0x0 : 0xFF000000);
+        }
       }
-      data = (uint8_t *)tmp;
-      // fall through to LG_CURSOR_COLOR
+      data = (const uint8_t *)rgba;
+      // fall through
       //
       // technically we should also create an XOR texture from the data but this
       // usage seems very rare in modern software.
 
     case LG_CURSOR_COLOR:
     {
+      if (cursor == LG_CURSOR_COLOR)
+      {
+        for(int y = 0; y < height; ++y)
+          memcpy(rgba + (size_t)y * (size_t)width,
+              data + (size_t)y * (size_t)pitch,
+              (size_t)width * sizeof(*rgba));
+        data = (const uint8_t *)rgba;
+      }
+
       glBindTexture(GL_TEXTURE_2D, this->textures[MOUSE_TEXTURE]);
       glPixelStorei(GL_UNPACK_ALIGNMENT , 4    );
       glPixelStorei(GL_UNPACK_ROW_LENGTH, width);
@@ -1169,19 +1209,28 @@ static void updateMouseShape(struct Inst * this)
     case LG_CURSOR_MONOCHROME:
     {
       const int hheight = height / 2;
-      uint32_t d[width * height];
       for(int y = 0; y < hheight; ++y)
+      {
+        const uint8_t * srcAnd =
+          data + (size_t)pitch * (size_t)y;
+        const uint8_t * srcXor =
+          data + (size_t)pitch * (size_t)(y + hheight);
         for(int x = 0; x < width; ++x)
         {
-          const uint8_t  * srcAnd  = data + (pitch * y) + (x / 8);
-          const uint8_t  * srcXor  = srcAnd + pitch * hheight;
           const uint8_t    mask    = 0x80 >> (x % 8);
-          const uint32_t   andMask = (*srcAnd & mask) ? 0xFFFFFFFF : 0xFF000000;
-          const uint32_t   xorMask = (*srcXor & mask) ? 0x00FFFFFF : 0x00000000;
+          const uint32_t   andMask =
+            (srcAnd[x / 8] & mask) ? 0xFFFFFFFF : 0xFF000000;
+          const uint32_t   xorMask =
+            (srcXor[x / 8] & mask) ? 0x00FFFFFF : 0x00000000;
+          const size_t andIndex =
+            (size_t)y * (size_t)width + (size_t)x;
+          const size_t xorIndex =
+            (size_t)(y + hheight) * (size_t)width + (size_t)x;
 
-          d[y * width + x                  ] = andMask;
-          d[y * width + x + width * hheight] = xorMask;
+          rgba[andIndex] = andMask;
+          rgba[xorIndex] = xorMask;
         }
+      }
 
       glBindTexture(GL_TEXTURE_2D, this->textures[MOUSE_TEXTURE]);
       glPixelStorei(GL_UNPACK_ALIGNMENT , 4    );
@@ -1196,7 +1245,7 @@ static void updateMouseShape(struct Inst * this)
         0      ,
         GL_RGBA,
         GL_UNSIGNED_BYTE,
-        d
+        rgba
       );
       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
diff --git a/client/src/render_queue.c b/client/src/render_queue.c
index 474679cf..40db2a54 100644
--- a/client/src/render_queue.c
+++ b/client/src/render_queue.c
@@ -494,16 +494,12 @@ static void setCommandSource(RenderCommand * cmd, RenderQueueSource source,
 
 static bool copyCursorImage(RenderCommand * cmd, const void * data)
 {
-  if (!data || cmd->cursorImage.width <= 0 ||
-      cmd->cursorImage.height <= 0 || cmd->cursorImage.pitch <= 0)
+  size_t size;
+  if (!data || !lg_rendererCursorValidate(cmd->cursorImage.type,
+        cmd->cursorImage.width, cmd->cursorImage.height,
+        cmd->cursorImage.pitch, &size))
     return false;
 
-  if ((size_t)cmd->cursorImage.height >
-      SIZE_MAX / (size_t)cmd->cursorImage.pitch)
-    return false;
-
-  const size_t size =
-    (size_t)cmd->cursorImage.height * (size_t)cmd->cursorImage.pitch;
   cmd->cursorImage.data = malloc(size);
   if (!cmd->cursorImage.data)
     return false;
diff --git a/client/tests/render_queue_test.c b/client/tests/render_queue_test.c
index 2353eefb..72cf544e 100644
--- a/client/tests/render_queue_test.c
+++ b/client/tests/render_queue_test.c
@@ -426,8 +426,16 @@ static void testPayload(void)
      1,  2,  3,  4,  5,  6,  7,  8,
      9, 10, 11, 12, 13, 14, 15, 16,
   };
-  uint8_t shape[] = { 11, 12, 13, 14, 15, 16, 17, 18 };
-  const uint8_t shapeExpected[] = { 11, 12, 13, 14, 15, 16, 17, 18 };
+  uint8_t shape[] =
+  {
+    11, 12, 13, 14, 15, 16, 17, 18,
+    19, 20, 21, 22, 23, 24, 25, 26,
+  };
+  const uint8_t shapeExpected[] =
+  {
+    11, 12, 13, 14, 15, 16, 17, 18,
+    19, 20, 21, 22, 23, 24, 25, 26,
+  };
   LGColorTransform color =
   {
     .flags        = LG_COLOR_TRANSFORM_MATRIX | LG_COLOR_TRANSFORM_LUT,
@@ -439,7 +447,7 @@ static void testPayload(void)
   renderQueue_sourceSwSurfaceDrawBitmap(RENDER_QUEUE_SOURCE_PRIMARY,
       generation, 0, 0, 2, 2, 8, bitmap, true);
   renderQueue_sourceCursorImage(RENDER_QUEUE_SOURCE_PRIMARY, generation,
-      LG_CURSOR_COLOR, 2, 2, 4, shape);
+      LG_CURSOR_COLOR, 2, 2, 8, shape);
   renderQueue_sourceCursorColorTransform(RENDER_QUEUE_SOURCE_PRIMARY,
       generation, &color);
   renderQueue_sourceCursorState(RENDER_QUEUE_SOURCE_PRIMARY, generation,
@@ -468,7 +476,7 @@ static void testPayload(void)
   CHECK(f.shapeType == LG_CURSOR_COLOR);
   CHECK(f.shapeWidth == 2);
   CHECK(f.shapeHeight == 2);
-  CHECK(f.shapePitch == 4);
+  CHECK(f.shapePitch == 8);
   CHECK(f.shapeSize == sizeof(shapeExpected));
   CHECK(memcmp(f.shape, shapeExpected, sizeof(shapeExpected)) == 0);
   CHECK(f.colorCount == 1);