## Description
There is a segment fault detected by AddressSanitizer

## System info
```
Ubuntu 20.04.2 LTS
clang version 12.0.0-++20210402082642+04ba60cfe598-1~exp1~20210402063359.71
MP4Box - GPAC version 1.1.0-DEV-rev1678-g92faba3ed-master
```

## Build command
```
./configure --static-mp4box --prefix=`realpath ./install` --enable-sanitizer --cc=clang --cxx=clang++
```

## crash command
```
MP4Box -frag 0 -out /dev/null poc_file
```

## Pocs
[poc.zip](https://github.com/gpac/gpac/files/7957290/poc.zip)

## Crash output
```
==36385==ERROR: AddressSanitizer: SEGV on unknown address (pc 0x000000931c87 bp 0x7ffe5ef10f50 sp 0x7ffe5ef10ee0 T0)
==36385==The signal is caused by a READ memory access.
==36385==Hint: this fault was caused by a dereference of a high value address (see register values below).  Disassemble the provided pc to learn which register was used.
    #0 0x931c87 in gf_isom_get_bitrate  /programs/mp4box/builds/build4/src/isomedia/isom_read.c:5400:19
    #1 0x18cdd84 in isor_declare_track  /programs/mp4box/builds/build4/src/filters/isoffin_load.c:1126:2
    #2 0x18d5d09 in isor_declare_objects  /programs/mp4box/builds/build4/src/filters/isoffin_load.c:1446:3
    #3 0xf74b36 in isoffin_initialize  /programs/mp4box/builds/build4/src/filters/isoffin_read.c:485:8
    #4 0xd7dd50 in gf_filter_new_finalize  /programs/mp4box/builds/build4/src/filter_core/filter.c:429:8
    #5 0xd7c3e6 in gf_filter_new  /programs/mp4box/builds/build4/src/filter_core/filter.c:383:7
    #6 0xd62574 in gf_fs_load_filter_internal  /programs/mp4box/builds/build4/src/filter_core/filter_session.c:1250:13
    #7 0xaa9c88 in gf_media_fragment_file  /programs/mp4box/builds/build4/src/media_tools/isom_tools.c:3784:6
    #8 0x4ebaff in mp4boxMain  /programs/mp4box/builds/build4/applications/mp4box/main.c:6455:7
    #9 0x7fd8cc90d0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #10 0x41ea6d in _start ( /programs/mp4box/builds/build4/bin/gcc/MP4Box+0x41ea6d)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV  /programs/mp4box/builds/build4/src/isomedia/isom_read.c:5400:19 in gf_isom_get_bitrate
==36385==ABORTING
```
There is a segment fault detected by AddressSanitizer
This is a GitHub Issue
repo:gpac
owner:gpac
Title : There is a segment fault detected by AddressSanitizer
Issue date:

--- start body ---
## Description
There is a segment fault detected by AddressSanitizer

## System info
```
Ubuntu 20.04.2 LTS
clang version 12.0.0-++20210402082642+04ba60cfe598-1~exp1~20210402063359.71
MP4Box - GPAC version 1.1.0-DEV-rev1678-g92faba3ed-master
```

## Build command
```
./configure --static-mp4box --prefix=`realpath ./install` --enable-sanitizer --cc=clang --cxx=clang++
```

## crash command
```
MP4Box -frag 0 -out /dev/null poc_file
```

## Pocs
[poc.zip](https://github.com/gpac/gpac/files/7957290/poc.zip)

## Crash output
```
==36385==ERROR: AddressSanitizer: SEGV on unknown address (pc 0x000000931c87 bp 0x7ffe5ef10f50 sp 0x7ffe5ef10ee0 T0)
==36385==The signal is caused by a READ memory access.
==36385==Hint: this fault was caused by a dereference of a high value address (see register values below).  Disassemble the provided pc to learn which register was used.
    #0 0x931c87 in gf_isom_get_bitrate  /programs/mp4box/builds/build4/src/isomedia/isom_read.c:5400:19
    #1 0x18cdd84 in isor_declare_track  /programs/mp4box/builds/build4/src/filters/isoffin_load.c:1126:2
    #2 0x18d5d09 in isor_declare_objects  /programs/mp4box/builds/build4/src/filters/isoffin_load.c:1446:3
    #3 0xf74b36 in isoffin_initialize  /programs/mp4box/builds/build4/src/filters/isoffin_read.c:485:8
    #4 0xd7dd50 in gf_filter_new_finalize  /programs/mp4box/builds/build4/src/filter_core/filter.c:429:8
    #5 0xd7c3e6 in gf_filter_new  /programs/mp4box/builds/build4/src/filter_core/filter.c:383:7
    #6 0xd62574 in gf_fs_load_filter_internal  /programs/mp4box/builds/build4/src/filter_core/filter_session.c:1250:13
    #7 0xaa9c88 in gf_media_fragment_file  /programs/mp4box/builds/build4/src/media_tools/isom_tools.c:3784:6
    #8 0x4ebaff in mp4boxMain  /programs/mp4box/builds/build4/applications/mp4box/main.c:6455:7
    #9 0x7fd8cc90d0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #10 0x41ea6d in _start ( /programs/mp4box/builds/build4/bin/gcc/MP4Box+0x41ea6d)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV  /programs/mp4box/builds/build4/src/isomedia/isom_read.c:5400:19 in gf_isom_get_bitrate
==36385==ABORTING
```
--- end body ---

A segmentation fault in the GPAC MP4Box application, specifically in the gf_isom_get_bitrate function, indicates a potential vulnerability that could be exploited to cause a Denial of Service (DoS) by providing a specially crafted input file. The crash occurs due to a memory access violation, which could lead to further exploitation if not handled properly.