A null pointer dereference vulnerability exists in gpac 1.1.0 in the gf_dump_vrml_dyn_field.isra function, which causes a segmentation fault and application crash.
Thanks for reporting your issue. Please make sure these boxes are checked before submitting your issue - thank you!

- [x] I looked for a similar issue and couldn't find any.
- [x] I tried with the latest version of GPAC. Installers available at http://gpac.io/downloads/gpac-nightly-builds/
- [x] 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/

A null pointer dereference was discovered in gf_dump_vrml_dyn_field.isra(). The vulnerability causes a segmentation fault and application crash.

**Version:**

```
MP4Box - GPAC version 1.1.0-DEV-revUNKNOWN_REV
(c) 2000-2021 Telecom Paris distributed under LGPL v2.1+ - http://gpac.io

Please cite our work in your research:
        GPAC Filters: https://doi.org/10.1145/3339825.3394929
        GPAC: https://doi.org/10.1145/1291233.1291452

GPAC Configuration:
Features: GPAC_CONFIG_LINUX GPAC_64_BITS GPAC_HAS_IPV6 GPAC_HAS_SOCK_UN GPAC_MINIMAL_ODF GPAC_HAS_QJS GPAC_HAS_JPEG GPAC_HAS_PNG GPAC_HAS_LINUX_DVB  GPAC_DISABLE_3D
```
**System information**
Ubuntu 20.04 focal, AMD EPYC 7742 64-Core @ 16x 2.25GHz

**command:**

```
./MP4Box -lsr ./poc4
```
[poc4.zip](https://github.com/gpac/gpac/files/7691639/poc4.zip)

**Result**

```
[iso file] extra box maxr found in hinf, deleting
[iso file] extra box maxr found in hinf, deleting
[iso file] Unknown box type 80rak in parent moov
[iso file] Incomplete box mdat - start 11495 size 860238
[iso file] Incomplete file while reading for dump - aborting parsing
[iso file] extra box maxr found in hinf, deleting
[iso file] extra box maxr found in hinf, deleting
[iso file] Unknown box type 80rak in parent moov
[iso file] Incomplete box mdat - start 11495 size 860238
[iso file] Incomplete file while reading for dump - aborting parsing
MPEG-4 BIFS Scene Parsing
Scene loaded - dumping 1 systems streams
[1]    414421 segmentation fault  ./MP4Box -lsr ./poc4
```

**gdb**

```
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7ac0797 in gf_dump_vrml_dyn_field.isra () from /root/fuckit/test/gpac-master/bin/gcc/libgpac.so.10
LEGEND: STACK | HEAP | CODE | DATA | RWX | RODATA
────────────────────────────────────────────[ REGISTERS ]─────────────────────────────────────────────
 RAX  0xa
 RBX  0x0
 RCX  0x0
 RDX  0x7ffff72bf040 ◂— 0x7ffff72bf040
 RDI  0x7fffffff6af0 —▸ 0x7ffff75a21e0 (funlockfile) ◂— endbr64
 RSI  0x0
 R8   0xffffffff
 R9   0xa
 R10  0x7ffff7e37a2a ◂— 0x3e73252f3c00223d /* '="' */
 R11  0x7ffff7df0c38 ◂— 0x6e776f6e6b6e75 /* 'unknown' */
 R12  0x0
 R13  0x0
 R14  0x5555555ded60 —▸ 0x5555555d43b0 ◂— 0x0
 R15  0x1
 RBP  0x3c
 RSP  0x7fffffff7060 ◂— 0x3000000010
 RIP  0x7ffff7ac0797 (gf_dump_vrml_dyn_field.isra+631) ◂— mov    eax, dword ptr [r12]
──────────────────────────────────────────────[ DISASM ]──────────────────────────────────────────────
 ► 0x7ffff7ac0797 <gf_dump_vrml_dyn_field.isra+631>    mov    eax, dword ptr [r12]
   0x7ffff7ac079b <gf_dump_vrml_dyn_field.isra+635>    test   eax, eax
   0x7ffff7ac079d <gf_dump_vrml_dyn_field.isra+637>    je     gf_dump_vrml_dyn_field.isra+720
       <gf_dump_vrml_dyn_field.isra+720>
    ↓
   0x7ffff7ac07f0 <gf_dump_vrml_dyn_field.isra+720>    mov    eax, dword ptr [rsp + 0x70]
   0x7ffff7ac07f4 <gf_dump_vrml_dyn_field.isra+724>    mov    rdi, qword ptr [r14 + 0x10]
   0x7ffff7ac07f8 <gf_dump_vrml_dyn_field.isra+728>    test   eax, eax
   0x7ffff7ac07fa <gf_dump_vrml_dyn_field.isra+730>    jne    gf_dump_vrml_dyn_field.isra+292
       <gf_dump_vrml_dyn_field.isra+292>
    ↓
   0x7ffff7ac0644 <gf_dump_vrml_dyn_field.isra+292>    lea    rsi, [rip + 0x35ac0b]
   0x7ffff7ac064b <gf_dump_vrml_dyn_field.isra+299>    xor    eax, eax
   0x7ffff7ac064d <gf_dump_vrml_dyn_field.isra+301>    call   gf_fprintf@plt                <gf_fprintf@plt>

   0x7ffff7ac0652 <gf_dump_vrml_dyn_field.isra+306>    jmp    gf_dump_vrml_dyn_field.isra+391
       <gf_dump_vrml_dyn_field.isra+391>
──────────────────────────────────────────────[ STACK ]───────────────────────────────────────────────
00:0000│ rsp 0x7fffffff7060 ◂— 0x3000000010
01:0008│     0x7fffffff7068 —▸ 0x5555555df880 ◂— 0x31646c6569665f /* '_field1' */
02:0010│     0x7fffffff7070 ◂— 0x0
03:0018│     0x7fffffff7078 ◂— 0x38b85a8f00
04:0020│     0x7fffffff7080 ◂— 0x0
05:0028│     0x7fffffff7088 ◂— 0x7aa5d2dbb85a8f00
06:0030│     0x7fffffff7090 ◂— 0x1
07:0038│     0x7fffffff7098 —▸ 0x7ffff7e27f46 ◂— 0x65646f6d73006325 /* '%c' */
────────────────────────────────────────────[ BACKTRACE ]─────────────────────────────────────────────
 ► f 0   0x7ffff7ac0797 gf_dump_vrml_dyn_field.isra+631
   f 1   0x7ffff7ac15d1 DumpProtos+305
   f 2   0x7ffff7abb389 gf_sm_dump_command_list+857
   f 3   0x7ffff7ac24fc gf_sm_dump+1116
   f 4   0x555555584418 dump_isom_scene+616
   f 5   0x55555557b42c mp4boxMain+9228
   f 6   0x7ffff75630b3 __libc_start_main+243
──────────────────────────────────────────────────────────────────────────────────────────────────────
pwndbg> bt
#0  0x00007ffff7ac0797 in gf_dump_vrml_dyn_field.isra () from /root/fuckit/test/gpac-master/bin/gcc/libgpac.so.10
#1  0x00007ffff7ac15d1 in DumpProtos () from /root/fuckit/test/gpac-master/bin/gcc/libgpac.so.10
#2  0x00007ffff7abb389 in gf_sm_dump_command_list () from /root/fuckit/test/gpac-master/bin/gcc/libgpac.so.10
#3  0x00007ffff7ac24fc in gf_sm_dump () from /root/fuckit/test/gpac-master/bin/gcc/libgpac.so.10
#4  0x0000555555584418 in dump_isom_scene ()
#5  0x000055555557b42c in mp4boxMain ()
#6  0x00007ffff75630b3 in __libc_start_main (main=0x55555556c420 <main>, argc=3, argv=0x7fffffffe1a8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffe198) at ../csu/libc-start.c:308
#7  0x000055555556c45e in _start ()
```


Null Pointer Dereference in gf_dump_vrml_dyn_field.isra()
This is a GitHub Issue
repo:gpac
owner:gpac
Title : Null Pointer Dereference in gf_dump_vrml_dyn_field.isra()
Issue date:

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

- [x] I looked for a similar issue and couldn't find any.
- [x] I tried with the latest version of GPAC. Installers available at http://gpac.io/downloads/gpac-nightly-builds/
- [x] 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/

A null pointer dereference was discovered in gf_dump_vrml_dyn_field.isra(). The vulnerability causes a segmentation fault and application crash.

**Version:**

```
MP4Box - GPAC version 1.1.0-DEV-revUNKNOWN_REV
(c) 2000-2021 Telecom Paris distributed under LGPL v2.1+ - http://gpac.io

Please cite our work in your research:
        GPAC Filters: https://doi.org/10.1145/3339825.3394929
        GPAC: https://doi.org/10.1145/1291233.1291452

GPAC Configuration:
Features: GPAC_CONFIG_LINUX GPAC_64_BITS GPAC_HAS_IPV6 GPAC_HAS_SOCK_UN GPAC_MINIMAL_ODF GPAC_HAS_QJS GPAC_HAS_JPEG GPAC_HAS_PNG GPAC_HAS_LINUX_DVB  GPAC_DISABLE_3D
```
**System information**
Ubuntu 20.04 focal, AMD EPYC 7742 64-Core @ 16x 2.25GHz

**command:**

```
./MP4Box -lsr ./poc4
```
[poc4.zip](https://github.com/gpac/gpac/files/7691639/poc4.zip)

**Result**

```
[iso file] extra box maxr found in hinf, deleting
[iso file] extra box maxr found in hinf, deleting
[iso file] Unknown box type 80rak in parent moov
[iso file] Incomplete box mdat - start 11495 size 860238
[iso file] Incomplete file while reading for dump - aborting parsing
[iso file] extra box maxr found in hinf, deleting
[iso file] extra box maxr found in hinf, deleting
[iso file] Unknown box type 80rak in parent moov
[iso file] Incomplete box mdat - start 11495 size 860238
[iso file] Incomplete file while reading for dump - aborting parsing
MPEG-4 BIFS Scene Parsing
Scene loaded - dumping 1 systems streams
[1]    414421 segmentation fault  ./MP4Box -lsr ./poc4
```

**gdb**

```
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7ac0797 in gf_dump_vrml_dyn_field.isra () from /root/fuckit/test/gpac-master/bin/gcc/libgpac.so.10
LEGEND: STACK | HEAP | CODE | DATA | RWX | RODATA
────────────────────────────────────────────[ REGISTERS ]─────────────────────────────────────────────
 RAX  0xa
 RBX  0x0
 RCX  0x0
 RDX  0x7ffff72bf040 ◂— 0x7ffff72bf040
 RDI  0x7fffffff6af0 —▸ 0x7ffff75a21e0 (funlockfile) ◂— endbr64
 RSI  0x0
 R8   0xffffffff
 R9   0xa
 R10  0x7ffff7e37a2a ◂— 0x3e73252f3c00223d /* '="' */
 R11  0x7ffff7df0c38 ◂— 0x6e776f6e6b6e75 /* 'unknown' */
 R12  0x0
 R13  0x0
 R14  0x5555555ded60 —▸ 0x5555555d43b0 ◂— 0x0
 R15  0x1
 RBP  0x3c
 RSP  0x7fffffff7060 ◂— 0x3000000010
 RIP  0x7ffff7ac0797 (gf_dump_vrml_dyn_field.isra+631) ◂— mov    eax, dword ptr [r12]
──────────────────────────────────────────────[ DISASM ]──────────────────────────────────────────────
 ► 0x7ffff7ac0797 <gf_dump_vrml_dyn_field.isra+631>    mov    eax, dword ptr [r12]
   0x7ffff7ac079b <gf_dump_vrml_dyn_field.isra+635>    test   eax, eax
   0x7ffff7ac079d <gf_dump_vrml_dyn_field.isra+637>    je     gf_dump_vrml_dyn_field.isra+720
       <gf_dump_vrml_dyn_field.isra+720>
    ↓
   0x7ffff7ac07f0 <gf_dump_vrml_dyn_field.isra+720>    mov    eax, dword ptr [rsp + 0x70]
   0x7ffff7ac07f4 <gf_dump_vrml_dyn_field.isra+724>    mov    rdi, qword ptr [r14 + 0x10]
   0x7ffff7ac07f8 <gf_dump_vrml_dyn_field.isra+728>    test   eax, eax
   0x7ffff7ac07fa <gf_dump_vrml_dyn_field.isra+730>    jne    gf_dump_vrml_dyn_field.isra+292
       <gf_dump_vrml_dyn_field.isra+292>
    ↓
   0x7ffff7ac0644 <gf_dump_vrml_dyn_field.isra+292>    lea    rsi, [rip + 0x35ac0b]
   0x7ffff7ac064b <gf_dump_vrml_dyn_field.isra+299>    xor    eax, eax
   0x7ffff7ac064d <gf_dump_vrml_dyn_field.isra+301>    call   gf_fprintf@plt                <gf_fprintf@plt>

   0x7ffff7ac0652 <gf_dump_vrml_dyn_field.isra+306>    jmp    gf_dump_vrml_dyn_field.isra+391
       <gf_dump_vrml_dyn_field.isra+391>
──────────────────────────────────────────────[ STACK ]───────────────────────────────────────────────
00:0000│ rsp 0x7fffffff7060 ◂— 0x3000000010
01:0008│     0x7fffffff7068 —▸ 0x5555555df880 ◂— 0x31646c6569665f /* '_field1' */
02:0010│     0x7fffffff7070 ◂— 0x0
03:0018│     0x7fffffff7078 ◂— 0x38b85a8f00
04:0020│     0x7fffffff7080 ◂— 0x0
05:0028│     0x7fffffff7088 ◂— 0x7aa5d2dbb85a8f00
06:0030│     0x7fffffff7090 ◂— 0x1
07:0038│     0x7fffffff7098 —▸ 0x7ffff7e27f46 ◂— 0x65646f6d73006325 /* '%c' */
────────────────────────────────────────────[ BACKTRACE ]─────────────────────────────────────────────
 ► f 0   0x7ffff7ac0797 gf_dump_vrml_dyn_field.isra+631
   f 1   0x7ffff7ac15d1 DumpProtos+305
   f 2   0x7ffff7abb389 gf_sm_dump_command_list+857
   f 3   0x7ffff7ac24fc gf_sm_dump+1116
   f 4   0x555555584418 dump_isom_scene+616
   f 5   0x55555557b42c mp4boxMain+9228
   f 6   0x7ffff75630b3 __libc_start_main+243
──────────────────────────────────────────────────────────────────────────────────────────────────────
pwndbg> bt
#0  0x00007ffff7ac0797 in gf_dump_vrml_dyn_field.isra () from /root/fuckit/test/gpac-master/bin/gcc/libgpac.so.10
#1  0x00007ffff7ac15d1 in DumpProtos () from /root/fuckit/test/gpac-master/bin/gcc/libgpac.so.10
#2  0x00007ffff7abb389 in gf_sm_dump_command_list () from /root/fuckit/test/gpac-master/bin/gcc/libgpac.so.10
#3  0x00007ffff7ac24fc in gf_sm_dump () from /root/fuckit/test/gpac-master/bin/gcc/libgpac.so.10
#4  0x0000555555584418 in dump_isom_scene ()
#5  0x000055555557b42c in mp4boxMain ()
#6  0x00007ffff75630b3 in __libc_start_main (main=0x55555556c420 <main>, argc=3, argv=0x7fffffffe1a8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffe198) at ../csu/libc-start.c:308
#7  0x000055555556c45e in _start ()
```


--- end body ---

A null pointer dereference vulnerability in the gf_dump_vrml_dyn_field.isra() function of GPAC version 1.1.0-DEV can lead to a segmentation fault and application crash. This issue occurs when the function attempts to access a null pointer, which can be exploited to cause a Denial of Service (DoS).