Bug 1269553 - (CVE-2015-8895) CVE-2015-8895 ImageMagick: Integer and buffer overflow in coders/icon.c
CVE-2015-8895 ImageMagick: Integer and buffer overflow in coders/icon.c
Status: NEW
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
medium Severity medium
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Assigned To: Red Hat Product Security
impact=moderate,public=20150528,repor...
: Security
Depends On: 1269556 1341777 1341778 1341779 1341780
Blocks: 1269554 1333419
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Reported: 2015-10-07 10:29 EDT by Adam Mariš
Modified: 2016-06-30 09:57 EDT (History)
17 users (show)

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Description Adam Mariš 2015-10-07 10:29:05 EDT
A vulnerability of integer overflow and subsequent buffer overflow was found in coders/icon.c. Memory is allocated based on the sum of a user-supplied value and a fixed value. That sum can overflow, causing only a small amount of memory to be allocated, while the program assumes more was allocated.

Vulnerable code:

icon_file.directory[i].offset=ReadBlobLSBLong(image);

On this line, it reads in 4byte value from the image and stores it in icon_file.directory[i].size.

length=icon_file.directory[i].size;
png=(unsigned char *) AcquireQuantumMemory(length+16,sizeof(*png));

Here the value of `length` is set to the value stored in icon_file.directory[i].size. At following line, 16 is added to `length` and allocates that amount of *png structures. However, if length+16 overflows (for example, length == 2^32 - 15), it will only allocate memory for a single *png. This is a problem, because the following lines assume that at least 16 bytes was allocated:

(void) CopyMagickMemory(png,"\211PNG\r\n\032\n\000\000\000\015",12);
png[12]=(unsigned char) icon_info.planes;
png[13]=(unsigned char) (icon_info.planes >> 8);
png[14]=(unsigned char) icon_info.bits_per_pixel;
png[15]=(unsigned char) (icon_info.bits_per_pixel >> 8);

And then the following line has a call to ReadBlob, and since length-16 will underflow (and the length is treated as a size_t), it will effectively execute a strcpy with the remaining data in the image file.

count=ReadBlob(image,length-16,png+16);

Detailed stacktrace with reproducer can be found here:

https://bugs.launchpad.net/ubuntu/+source/imagemagick/+bug/1459747

Upstream patch (only the "coders/icon.c" subsection of the commit is relevant):

https://github.com/ImageMagick/ImageMagick/commit/0f6fc2d5bf8f500820c3dbcf0d23ee14f2d9f734

CVE request:

http://seclists.org/oss-sec/2015/q4/45
Comment 1 Adam Mariš 2015-10-07 10:32:58 EDT
Created ImageMagick tracking bugs for this issue:

Affects: fedora-all [bug 1269556]
Comment 4 errata-xmlrpc 2016-06-16 18:47:37 EDT
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6
  Red Hat Enterprise Linux 7

Via RHSA-2016:1237 https://access.redhat.com/errata/RHSA-2016:1237

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