CVE-2017-13776: GraphicsMagick 1.3.26 Denial of Service issue in ReadXBMImage() in coders/xbm.c

["孙浩" <tony.sh () alibaba-inc com>]

Hi all.
Description:graphicsmagick is a collection of tools and libraries for many image formats.
We found a denial of service (DoS) issue in xbm.c at line 322, GraphicsMagick-1.3.26.The vulnerable code snippet is 
shown as below.    322     for (i=0; i < (long) (bytes_per_line*image->rows); i++)
    323     {
    324       value=XBMInteger(image,hex_digits);
    325       *p++=(unsigned char) value;
    326     }When a crafted XBM image file, which claims large image->rows and image->columns but does not contains 
sufficient backing data, is provided,the
 loop at line 322 would consume huge CPU and memroy 
resources, since there is no EOF (End of File) check inside the loop.It is worth noting that variable bytes_per_line is 
computed based on image->columns earlier.In our test, we used a machine with Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz, 
4 CPU cores and 16GB RAM.This bug casued 100% CPU and up to 2GB RAM consumption.
This process lasted for about 6 minutes.
Affected version:
1.3.26

Fixed version:
N/A

Commit fix:
http://hg.code.sf.net/p/graphicsmagick/code/rev/233a720bfd5eCredit:
This bug was discovered by Xiaohei and Wangchu from Alibaba Security Team.

CVE:
CVE-2017-13776

Reproducer:
https://github.com/shqking/graphicsmagick-poc/blob/master/poc-322.xbmThe command we was using is     gm convert 
poc-322.xbm test.jpg

Timeline:
2017-08-24: bug discovered and reported to upstream privately
2017-08-26: upstream released a fix
2017-08-30: CVE assigned