The XWD image (X Window System window dumping file) parsing component in ImageMagick 7.0.8-41 Q16 allows attackers to cause a denial-of-service (application crash resulting from an out-of-bounds Read) in ReadXWDImage in coders/xwd.c by crafting a corrupted XWD image file, a different vulnerability than CVE-2019-11472.
### Prerequisites

- [x] I have written a descriptive issue title
- [x] I have verified that I am using the latest version of ImageMagick
- [x] I have searched [open](https://github.com/ImageMagick/ImageMagick/issues) and [closed](https://github.com/ImageMagick/ImageMagick/issues?q=is%3Aissue+is%3Aclosed) issues to ensure it has not already been reported

### Description
When reading on XWD files ImageMagick(112760b26) may suffer from a crash caused by invalid memory read.

### Steps to Reproduce
- run `identity -verbose  $FILE` or `convert $FILE /dev/null`.
- POCs:
https://github.com/ntu-sec/pocs/raw/master/imagemagick/112760b26/crashes/read_xwd.c:573_1.xwd
https://github.com/ntu-sec/pocs/raw/master/imagemagick/112760b26/crashes/read_xwd.c:573_2.xwd
- A report from an AddressSanitizer copmiled ImageMagick is like this:
```
ASAN:DEADLYSIGNAL
=================================================================
==9749==ERROR: AddressSanitizer: SEGV on unknown address 0x6020060639d6 (pc 0x7f2e39bbca6a bp 0x7ffc674ae0d0 sp 0x7ffc674ad338 T0)
==9749==The signal is caused by a READ memory access.
    #0 0x7f2e39bbca69  (/usr/lib/x86_64-linux-gnu/libX11.so.6+0x27a69)
    #1 0x7f2e40f77c89 in ReadXWDImage /home/hongxu/work/imagemagick/ImageMagick-asan/coders/xwd.c:573:21
    #2 0x7f2e405308c9 in ReadImage /home/hongxu/work/imagemagick/ImageMagick-asan/MagickCore/constitute.c:547:15
    #3 0x7f2e405342d4 in ReadImages /home/hongxu/work/imagemagick/ImageMagick-asan/MagickCore/constitute.c:917:9
    #4 0x7f2e3fac69a4 in ConvertImageCommand /home/hongxu/work/imagemagick/ImageMagick-asan/MagickWand/convert.c:644:18
    #5 0x7f2e3fcae021 in MagickCommandGenesis /home/hongxu/work/imagemagick/ImageMagick-asan/MagickWand/mogrify.c:185:14
    #6 0x50c8a7 in MagickMain /home/hongxu/work/imagemagick/ImageMagick-asan/utilities/magick.c:149:10
    #7 0x50c301 in main /home/hongxu/work/imagemagick/ImageMagick-asan/utilities/magick.c:180:10
    #8 0x7f2e3891fb96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310
    #9 0x41ce19 in _start (/home/hongxu/work/imagemagick/ImageMagick-asan/install/bin/magick+0x41ce19)
```
- Other information available [here](https://github.com/ntu-sec/pocs/tree/master/imagemagick/112760b26/crashes).

### System Configuration
- ImageMagick version: 7.0.8-41 Q16 x86_64 2019-04-20
- Environment (Operating system, version and so on): Ubuntu 18.04 LTS x86_64
- Additional information: This was firstly detected when fuzzing GraphicsMagick.
AddressSanitizer: Invalid read at xwd.c:573
This is a GitHub Issue
repo:ImageMagick
owner:ImageMagick
Title : AddressSanitizer: Invalid read at xwd.c:573
Issue date:

--- start body ---
### Prerequisites

- [x] I have written a descriptive issue title
- [x] I have verified that I am using the latest version of ImageMagick
- [x] I have searched [open](https://github.com/ImageMagick/ImageMagick/issues) and [closed](https://github.com/ImageMagick/ImageMagick/issues?q=is%3Aissue+is%3Aclosed) issues to ensure it has not already been reported

### Description
When reading on XWD files ImageMagick(112760b26) may suffer from a crash caused by invalid memory read.

### Steps to Reproduce
- run `identity -verbose  $FILE` or `convert $FILE /dev/null`.
- POCs:
https://github.com/ntu-sec/pocs/raw/master/imagemagick/112760b26/crashes/read_xwd.c:573_1.xwd
https://github.com/ntu-sec/pocs/raw/master/imagemagick/112760b26/crashes/read_xwd.c:573_2.xwd
- A report from an AddressSanitizer copmiled ImageMagick is like this:
```
ASAN:DEADLYSIGNAL
=================================================================
==9749==ERROR: AddressSanitizer: SEGV on unknown address 0x6020060639d6 (pc 0x7f2e39bbca6a bp 0x7ffc674ae0d0 sp 0x7ffc674ad338 T0)
==9749==The signal is caused by a READ memory access.
    #0 0x7f2e39bbca69  (/usr/lib/x86_64-linux-gnu/libX11.so.6+0x27a69)
    #1 0x7f2e40f77c89 in ReadXWDImage /home/hongxu/work/imagemagick/ImageMagick-asan/coders/xwd.c:573:21
    #2 0x7f2e405308c9 in ReadImage /home/hongxu/work/imagemagick/ImageMagick-asan/MagickCore/constitute.c:547:15
    #3 0x7f2e405342d4 in ReadImages /home/hongxu/work/imagemagick/ImageMagick-asan/MagickCore/constitute.c:917:9
    #4 0x7f2e3fac69a4 in ConvertImageCommand /home/hongxu/work/imagemagick/ImageMagick-asan/MagickWand/convert.c:644:18
    #5 0x7f2e3fcae021 in MagickCommandGenesis /home/hongxu/work/imagemagick/ImageMagick-asan/MagickWand/mogrify.c:185:14
    #6 0x50c8a7 in MagickMain /home/hongxu/work/imagemagick/ImageMagick-asan/utilities/magick.c:149:10
    #7 0x50c301 in main /home/hongxu/work/imagemagick/ImageMagick-asan/utilities/magick.c:180:10
    #8 0x7f2e3891fb96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310
    #9 0x41ce19 in _start (/home/hongxu/work/imagemagick/ImageMagick-asan/install/bin/magick+0x41ce19)
```
- Other information available [here](https://github.com/ntu-sec/pocs/tree/master/imagemagick/112760b26/crashes).

### System Configuration
- ImageMagick version: 7.0.8-41 Q16 x86_64 2019-04-20
- Environment (Operating system, version and so on): Ubuntu 18.04 LTS x86_64
- Additional information: This was firstly detected when fuzzing GraphicsMagick.
--- end body ---
