A Pointer Dereference Vulnerability exits in GPAC 1.0.1 in the gf_list_count function, which causes a Denial of Service.
Thanks for reporting your issue. Please make sure these boxes are checked before submitting your issue - thank you!

- [Yes ] I looked for a similar issue and couldn't find any.
- [ Yes] I tried with the latest version of GPAC. Installers available at http://gpac.io/downloads/gpac-nightly-builds/
- [ Yes] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...). I can share files anonymously with this dropbox: https://www.mediafire.com/filedrop/filedrop_hosted.php?drop=eec9e058a9486fe4e99c33021481d9e1826ca9dbc242a6cfaab0fe95da5e5d95

Detailed guidelines: http://gpac.io/2013/07/16/how-to-file-a-bug-properly/

**Version:**
```
./MP4Box -version
```

**command:**
```
./bin/gcc/MP4Box -hint POC3
```
[POC3.zip](https://github.com/gpac/gpac/files/7763770/POC3.zip)


**Result**
```
segmentation fault
```
**bt**

```Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7773949 in gf_list_count () from /home/zxq/CVE_testing/source/gpac/bin/gcc/libgpac.so.10
LEGEND: STACK | HEAP | CODE | DATA | RWX | RODATA
───────────────────────────────────────────────────────────────────────[ REGISTERS ]────────────────────────────────────────────────────────────────────────
 RAX  0x5555555e0010 ◂— 0x7374626c /* 'lbts' */
 RBX  0x15
 RCX  0x5555555e8230 ◂— 0x33483
 RDX  0x2315
 RDI  0x5569555e0124
 RSI  0x15
 R8   0x5555555e8230 ◂— 0x33483
 R9   0x7fffffff7f00 ◂— 0x158
 R10  0x7ffff76d927a ◂— 'gf_isom_box_size'
 R11  0x7ffff76a0be0 (main_arena+96) —▸ 0x5555555e8380 ◂— 0x14
 R12  0x5555555e29d0 ◂— 0x1473747378
 R13  0x5555555e0530 ◂— 0x73747363 /* 'csts' */
 R14  0x5555555e81f0 ◂— 0x636f3634 /* '46oc' */
 R15  0x1
 RBP  0x5555555dfc30 ◂— 0x6d646961 /* 'aidm' */
 RSP  0x7fffffff7f28 —▸ 0x7ffff79286ed (Media_IsSelfContained+61) ◂— cmp    ebx, eax
 RIP  0x7ffff7773949 (gf_list_count+9) ◂— mov    eax, dword ptr [rdi + 8]
─[ DISASM ]─
 ► 0x7ffff7773949 <gf_list_count+9>     mov    eax, dword ptr [rdi + 8]
   0x7ffff777394c <gf_list_count+12>    ret    
 
   0x7ffff777394d <gf_list_count+13>    nop    dword ptr [rax]
   0x7ffff7773950 <gf_list_count+16>    xor    eax, eax
   0x7ffff7773952 <gf_list_count+18>    ret    
 
   0x7ffff7773953                       nop    word ptr cs:[rax + rax]
   0x7ffff777395e                       nop    
   0x7ffff7773960 <gf_list_get>         endbr64 
   0x7ffff7773964 <gf_list_get+4>       test   rdi, rdi
   0x7ffff7773967 <gf_list_get+7>       je     gf_list_get+32                <gf_list_get+32>
    ↓
   0x7ffff7773980 <gf_list_get+32>      xor    eax, eax
[ STACK ]
00:0000│ rsp 0x7fffffff7f28 —▸ 0x7ffff79286ed (Media_IsSelfContained+61) ◂— cmp    ebx, eax
01:0008│     0x7fffffff7f30 —▸ 0x5555555e2974 ◂— 0x140000232b /* '+#' */
02:0010│     0x7fffffff7f38 —▸ 0x5555555e81f0 ◂— 0x636f3634 /* '46oc' */
03:0018│     0x7fffffff7f40 ◂— 0x14
04:0020│     0x7fffffff7f48 —▸ 0x7ffff790ffcb (shift_chunk_offsets.part+75) ◂— test   eax, eax
05:0028│     0x7fffffff7f50 —▸ 0x5555555dfc30 ◂— 0x6d646961 /* 'aidm' */
06:0030│     0x7fffffff7f58 —▸ 0x5555555e0530 ◂— 0x73747363 /* 'csts' */
07:0038│     0x7fffffff7f60 ◂— 0x0
──────[ BACKTRACE ]────
 ► f 0   0x7ffff7773949 gf_list_count+9
   f 1   0x7ffff79286ed Media_IsSelfContained+61
   f 2   0x7ffff790ffcb shift_chunk_offsets.part+75
   f 3   0x7ffff79103a7 inplace_shift_moov_meta_offsets+231
   f 4   0x7ffff7910e3c inplace_shift_mdat+732
   f 5   0x7ffff7915009 WriteToFile+2713
   f 6   0x7ffff7906432 gf_isom_write+370
   f 7   0x7ffff79064b8 gf_isom_close+24



```
Untrusted Pointer Dereference in gf_list_count ()
This is a GitHub Issue
repo:gpac
owner:gpac
Title : Untrusted Pointer Dereference in gf_list_count ()
Issue date:

--- start body ---
Thanks for reporting your issue. Please make sure these boxes are checked before submitting your issue - thank you!

- [Yes ] I looked for a similar issue and couldn't find any.
- [ Yes] I tried with the latest version of GPAC. Installers available at http://gpac.io/downloads/gpac-nightly-builds/
- [ Yes] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...). I can share files anonymously with this dropbox: https://www.mediafire.com/filedrop/filedrop_hosted.php?drop=eec9e058a9486fe4e99c33021481d9e1826ca9dbc242a6cfaab0fe95da5e5d95

Detailed guidelines: http://gpac.io/2013/07/16/how-to-file-a-bug-properly/

**Version:**
```
./MP4Box -version
```

**command:**
```
./bin/gcc/MP4Box -hint POC3
```
[POC3.zip](https://github.com/gpac/gpac/files/7763770/POC3.zip)


**Result**
```
segmentation fault
```
**bt**

```Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7773949 in gf_list_count () from /home/zxq/CVE_testing/source/gpac/bin/gcc/libgpac.so.10
LEGEND: STACK | HEAP | CODE | DATA | RWX | RODATA
───────────────────────────────────────────────────────────────────────[ REGISTERS ]────────────────────────────────────────────────────────────────────────
 RAX  0x5555555e0010 ◂— 0x7374626c /* 'lbts' */
 RBX  0x15
 RCX  0x5555555e8230 ◂— 0x33483
 RDX  0x2315
 RDI  0x5569555e0124
 RSI  0x15
 R8   0x5555555e8230 ◂— 0x33483
 R9   0x7fffffff7f00 ◂— 0x158
 R10  0x7ffff76d927a ◂— 'gf_isom_box_size'
 R11  0x7ffff76a0be0 (main_arena+96) —▸ 0x5555555e8380 ◂— 0x14
 R12  0x5555555e29d0 ◂— 0x1473747378
 R13  0x5555555e0530 ◂— 0x73747363 /* 'csts' */
 R14  0x5555555e81f0 ◂— 0x636f3634 /* '46oc' */
 R15  0x1
 RBP  0x5555555dfc30 ◂— 0x6d646961 /* 'aidm' */
 RSP  0x7fffffff7f28 —▸ 0x7ffff79286ed (Media_IsSelfContained+61) ◂— cmp    ebx, eax
 RIP  0x7ffff7773949 (gf_list_count+9) ◂— mov    eax, dword ptr [rdi + 8]
─[ DISASM ]─
 ► 0x7ffff7773949 <gf_list_count+9>     mov    eax, dword ptr [rdi + 8]
   0x7ffff777394c <gf_list_count+12>    ret    
 
   0x7ffff777394d <gf_list_count+13>    nop    dword ptr [rax]
   0x7ffff7773950 <gf_list_count+16>    xor    eax, eax
   0x7ffff7773952 <gf_list_count+18>    ret    
 
   0x7ffff7773953                       nop    word ptr cs:[rax + rax]
   0x7ffff777395e                       nop    
   0x7ffff7773960 <gf_list_get>         endbr64 
   0x7ffff7773964 <gf_list_get+4>       test   rdi, rdi
   0x7ffff7773967 <gf_list_get+7>       je     gf_list_get+32                <gf_list_get+32>
    ↓
   0x7ffff7773980 <gf_list_get+32>      xor    eax, eax
[ STACK ]
00:0000│ rsp 0x7fffffff7f28 —▸ 0x7ffff79286ed (Media_IsSelfContained+61) ◂— cmp    ebx, eax
01:0008│     0x7fffffff7f30 —▸ 0x5555555e2974 ◂— 0x140000232b /* '+#' */
02:0010│     0x7fffffff7f38 —▸ 0x5555555e81f0 ◂— 0x636f3634 /* '46oc' */
03:0018│     0x7fffffff7f40 ◂— 0x14
04:0020│     0x7fffffff7f48 —▸ 0x7ffff790ffcb (shift_chunk_offsets.part+75) ◂— test   eax, eax
05:0028│     0x7fffffff7f50 —▸ 0x5555555dfc30 ◂— 0x6d646961 /* 'aidm' */
06:0030│     0x7fffffff7f58 —▸ 0x5555555e0530 ◂— 0x73747363 /* 'csts' */
07:0038│     0x7fffffff7f60 ◂— 0x0
──────[ BACKTRACE ]────
 ► f 0   0x7ffff7773949 gf_list_count+9
   f 1   0x7ffff79286ed Media_IsSelfContained+61
   f 2   0x7ffff790ffcb shift_chunk_offsets.part+75
   f 3   0x7ffff79103a7 inplace_shift_moov_meta_offsets+231
   f 4   0x7ffff7910e3c inplace_shift_mdat+732
   f 5   0x7ffff7915009 WriteToFile+2713
   f 6   0x7ffff7906432 gf_isom_write+370
   f 7   0x7ffff79064b8 gf_isom_close+24



```
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