If the title doesn't sound interesting it's probably best to skip this one. An amazing bit of work and evil intent.
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JBIG2 doesn't have scripting capabilities, but when combined with a vulnerability, it does have the ability to emulate circuits of arbitrary logic gates operating on arbitrary memory. So why not just use that to build your own computer architecture and script that!? That's exactly what this exploit does. Using over 70,000 segment commands defining logical bit operations, they define a small computer architecture with features such as registers and a full 64-bit adder and comparator which they use to search memory and perform arithmetic operations. It's not as fast as Javascript, but it's fundamentally computationally equivalent.
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a tip of the hat to Matt
Article contains a fascinating link http://www.dkriesel.com/en/blog/2013/0802_xerox-workcentres_are_switching_written_numbers_when_scanning where image compression *glyphs* result in seriously dangerous reconstruction errors.
Posted by: greg b | December 16, 2021 at 16:13