CVE-2021-36414

A heap-buffer-overflow has occurred when running program MP4Box,which leads to a Deny of Service caused by dividing zero without sanity check,this can reproduce on the lattest commit.

Here: the main problem is dividing into zero

Assigning block_size:

block_size = ent ? ent->sampleDelta : 160;

• This line uses the conditional (ternary) operator to assign a value to block_size.
• It checks if ent is not NULL.
  • If ent is valid (i.e., not NULL), block_size is assigned the value of ent->sampleDelta.
  • If ent is NULL, block_size is assigned a default value of 160.

Fix

https://github.com/gpac/gpac/commit/6007c7145eb0fcd29fe05b6e5983a065b42c6b21

Way of finding

Bug find out by fuzzing checks.

https://github.com/gpac/gpac/issues/1840