diff --git a/unix/x0vncserver/Image.cxx b/unix/x0vncserver/Image.cxx
index f998c6a..fb9dbd4 100644
--- a/unix/x0vncserver/Image.cxx
+++ b/unix/x0vncserver/Image.cxx
@@ -80,6 +80,14 @@ void Image::Init(int width, int height)
   xim = XCreateImage(dpy, vis, DefaultDepth(dpy, DefaultScreen(dpy)),
                      ZPixmap, 0, 0, width, height, BitmapPad(dpy), 0);

+  if (xim->bytes_per_line <= 0 ||
+      xim->height <= 0 ||
+      xim->height >= INT_MAX / xim->bytes_per_line) {
+    vlog.error("Invalid display size");
+    XDestroyImage(xim);
+    exit(1);
+  }
+
   xim->data = (char *)malloc(xim->bytes_per_line * xim->height);
   if (xim->data == NULL) {
     vlog.error("malloc() failed");
@@ -256,6 +264,17 @@ void ShmImage::Init(int width, int height, const XVisualInfo *vinfo)
     return;
   }

+  if (xim->bytes_per_line <= 0 ||
+      xim->height <= 0 ||
+      xim->height >= INT_MAX / xim->bytes_per_line) {
+    vlog.error("Invalid display size");
+    XDestroyImage(xim);
+    xim = NULL;
+    delete shminfo;
+    shminfo = NULL;
+    return;
+  }
+
   shminfo->shmid = shmget(IPC_PRIVATE,
                           xim->bytes_per_line * xim->height,
                           IPC_CREAT|0777);
diff --git a/vncviewer/PlatformPixelBuffer.cxx b/vncviewer/PlatformPixelBuffer.cxx
index a2b506d..9266d9f 100644
--- a/vncviewer/PlatformPixelBuffer.cxx
+++ b/vncviewer/PlatformPixelBuffer.cxx
@@ -49,6 +49,15 @@ PlatformPixelBuffer::PlatformPixelBuffer(int width, int height) :
     if (!xim)
       throw rdr::Exception("XCreateImage");

+    if (xim->bytes_per_line <= 0 ||
+       xim->height <= 0 ||
+       xim->height >= INT_MAX / xim->bytes_per_line) {
+      if (xim)
+       XDestroyImage(xim);
+      xim = NULL;
+      throw rdr::Exception("Invalid display size");
+    }
+
     xim->data = (char*)malloc(xim->bytes_per_line * xim->height);
     if (!xim->data)
       throw rdr::Exception("malloc");
@@ -152,6 +161,16 @@ bool PlatformPixelBuffer::setupShm()
   if (!xim)
     goto free_shminfo;

+  if (xim->bytes_per_line <= 0 ||
+      xim->height <= 0 ||
+      xim->height >= INT_MAX / xim->bytes_per_line) {
+    XDestroyImage(xim);
+    xim = NULL;
+    delete shminfo;
+    shminfo = NULL;
+    throw rdr::Exception("Invalid display size");
+  }
+
   shminfo->shmid = shmget(IPC_PRIVATE,
                           xim->bytes_per_line * xim->height,
                           IPC_CREAT|0600);