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T1 Font Integer Overflow
The T1 Font Integer Overflow (A.K.A DejaVu as it is very similar to the Malformed CFF Vulnerability[1]) is a vulnerability used in Saffron.
Credit for Exploitation
Description
When dealing with op_callothersubr, arg_cnt is defined as an integer. arg_cnt is read from decoder‑>stack, which could be set to 0xfea50000 by charstring "fb ef". And this will bypass stack checking. Then "top ‑= arg_cnt" will make top point to data outside of decoder‑>stack. Actually it points to decoder‑>parse_callback. decoder->parse_callback address minus default address of that function to get ASLR offset. That's how it bypass ASLR.
This vulnerability was actually addressed by Apple in Template:Wp/Security Update 2011-004, but a fix was never pushed to iOS. Its CVE identifier is CVE-2011-0202.
