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ImageMagick heap overflow and out of bounds read

Recently the ImageTragick vulnerability shed some light on the security status of ImageMagick.

This made me wonder how resilient to fuzzing ImageMagick is these days. It's pretty much a posterchild example for a good fuzzing target: Lots of supported complex binary file formats.

I already did some fuzzing on ImageMagick, but as far as I remember that was before I used american fuzzy lop and was done with zzuf. I was also aware that others did some more thorough fuzzing on ImageMagick.

What I did now was relatively simple: I took a trivial, few pixels PNG and used ImageMagick's "convert" tool to convert it into all file formats that have both read and write support in ImageMagick. I used that to run a fuzzing job with afl and asan. By design ImageMagick will sometimes do huge memory allocations, these can be prevented by setting limits for the width, height and memory usage in the policy.xml file.

I discovered one heap buffer overflow in the PICT parser and one heap out of bounds read in the PSD parser. Given how big the attack surface is this is not terrible, but it shows that despite previous efforts there's still potential to fuzz ImageMagick.

Sample file for heap buffer overflow in WritePixelCachePixels() (PICT format)
Git commit / fix

Sample file for heap out of bounds read in PushShortPixel() (PSD format)
Git commit / fix

Both issues have been fixed in the versions 6.9.4-0 and 7.0.1-2. In the meantime new versions (6.9.4-1, 7.0.1-3) came out that, as far as I understand the ChangeLog, remove another potential vector for the ImageTragick vulnerabilities, so you should preferrably update to those.


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