Source: https://code.google.com/p/google-security-research/issues/detail?id=426&can=1&q=label%3AProduct-Flash%20modified-after%3A2015%2F8%2F17&sort=id

To reproduce, host the attached files appropriately, and:

http://localhost/LoadMP4.swf?file=crash3006694.flv

If there is no crash at first, refresh the page a few times.

With a debugger attached to 64-bit Flash in Chrome Linux, the crash manifests like this:

=> 0x00007f7779846eee:	mov    %ax,(%rdi,%rdx,2)

rax            0xff69
rdi            0x7f7778b70000
rdx            0x160b

7f777861e000-7f7778b72000 rw-p 00000000 00:00 0 
7f7778b72000-7f7779228000 ---p 00000000 00:00 0 

It looks like an indexing error; the rdi "base" address is in bounds but add on 2*rdx and the address is not in bounds.

Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/37880.zip