## Description
A NULL Pointer Dereference was discovered in setnmap() at cmds.c:2303. The vulnerability causes a segmentation fault and application crash.
**version**
```
./ftp --version
ftp (GNU inetutils) 2.2.16-cf091
Copyright (C) 2021 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <
https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Written by many authors.
```
**System information**
Ubuntu 20.04 focal, AMD EPYC 7742 64-Core @ 16x 2.25GHz
## Proof of Concept
**poc**
```
base64 poc
bm1hIBjyAoHzCcvLArnD/sreCvgmMwoKAPUKEBoKEAAKDgAAAIDn5+fn5wAABADn5+foA+f4FJ0r
CgoKCgoK538Kubn/gAArCgp/CgoKCgoKQn8K1rn/gAAKCgp/CgoKAN0=
```
**command:**
```
./ftp < ./poc
```
**Result**
```
./ftp < ./poc
[1] 728662 segmentation fault ./ftp < ./poc
```
**gdb**
```
Program received signal SIGSEGV, Segmentation fault.
0x000055555555ec9d in setnmap (argc=3, argv=0x55555557e680 <margv>) at cmds.c:2303
2303 *cp = '\0';
LEGEND: STACK | HEAP | CODE | DATA | RWX | RODATA
────────────────────────────────────────────[ REGISTERS ]─────────────────────────────────────────────
RAX 0x0
RBX 0x5555555702c0 (__libc_csu_init) ◂— endbr64
RCX 0x4
RDX 0x0
RDI 0x555555582aa0 ◂— 0x8102f21820616d6e
RSI 0x20
R8 0x555555583620 ◂— 0x8102f21800616d6e /* 'nma' */
R9 0x7ffff7f5a010 (main_arena+1168) —▸ 0x7ffff7f5a000 (main_arena+1152) —▸ 0x7ffff7f59ff0 (main_arena+1136) —▸ 0x7ffff7f59fe0 (main_arena+1120) —▸ 0x7ffff7f59fd0 (main_arena+1104) ◂— ...
R10 0x555555580010 ◂— 0x0
R11 0x7ffff7f59be0 (main_arena+96) —▸ 0x5555555851a0 ◂— 0x0
R12 0x555555559f30 (_start) ◂— endbr64
R13 0x7fffffffe210 ◂— 0x1
R14 0x0
R15 0x0
RBP 0x7fffffffe060 —▸ 0x7fffffffe0a0 —▸ 0x7fffffffe120 ◂— 0x0
RSP 0x7fffffffe040 —▸ 0x55555557e680 (margv) —▸ 0x555555583620 ◂— 0x8102f21800616d6e /* 'nma' */
RIP 0x55555555ec9d (setnmap+258) ◂— mov byte ptr [rax], 0
──────────────────────────────────────────────[ DISASM ]──────────────────────────────────────────────
► 0x55555555ec9d <setnmap+258> mov byte ptr [rax], 0
0x55555555eca0 <setnmap+261> mov rax, qword ptr [rip + 0x1ae49] <0x555555579af0>
0x55555555eca7 <setnmap+268> mov rdi, rax
0x55555555ecaa <setnmap+271> call rpl_free <rpl_free>
0x55555555ecaf <setnmap+276> mov rax, qword ptr [rip + 0x1f98a] <0x55555557e640>
0x55555555ecb6 <setnmap+283> mov rdi, rax
0x55555555ecb9 <setnmap+286> call strdup@plt <strdup@plt>
0x55555555ecbe <setnmap+291> mov qword ptr [rip + 0x1ae2b], rax <0x555555579af0>
0x55555555ecc5 <setnmap+298> jmp setnmap+301 <setnmap+301>
0x55555555ecc7 <setnmap+300> nop
0x55555555ecc8 <setnmap+301> add qword ptr [rbp - 8], 1
──────────────────────────────────────────[ SOURCE (CODE) ]───────────────────────────────────────────
In file: /root/disk2/fuzzing/inetutils/inetutils/ftp/cmds.c
2298 while (*++cp == ' ')
2299 continue;
2300 altarg = cp;
2301 cp = strchr (altarg, ' ');
2302 }
► 2303 *cp = '\0';
2304
2305 free (mapin);
2306 mapin = strdup (altarg);
2307
2308 while (*++cp == ' ')
──────────────────────────────────────────────[ STACK ]───────────────────────────────────────────────
00:0000│ rsp 0x7fffffffe040 —▸ 0x55555557e680 (margv) —▸ 0x555555583620 ◂— 0x8102f21800616d6e /* 'nma' */
01:0008│ 0x7fffffffe048 ◂— 0x355583620
02:0010│ 0x7fffffffe050 —▸ 0x5555555796c0 (cmdtab+2464) ◂— 0x0
03:0018│ 0x7fffffffe058 ◂— 0x0
04:0020│ rbp 0x7fffffffe060 —▸ 0x7fffffffe0a0 —▸ 0x7fffffffe120 ◂— 0x0
05:0028│ 0x7fffffffe068 —▸ 0x555555566a09 (cmdscanner+633) ◂— mov eax, dword ptr [rip + 0x17bf5]
06:0030│ 0x7fffffffe070 ◂— 0x0
07:0038│ 0x7fffffffe078 ◂— 0x1c54c7100
────────────────────────────────────────────[ BACKTRACE ]─────────────────────────────────────────────
► f 0 0x55555555ec9d setnmap+258
f 1 0x555555566a09 cmdscanner+633
f 2 0x55555556665a main+929
f 3 0x7ffff7d950b3 __libc_start_main+243
──────────────────────────────────────────────────────────────────────────────────────────────────────
pwndbg> bt
#0 0x000055555555ec9d in setnmap (argc=3, argv=0x55555557e680 <margv>) at cmds.c:2303
#1 0x0000555555566a09 in cmdscanner (top=1) at main.c:461
#2 0x000055555556665a in main (argc=0, argv=0x7fffffffe220) at main.c:310
#3 0x00007ffff7d950b3 in __libc_start_main (main=0x5555555662b9 <main>, argc=1, argv=0x7fffffffe218, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffe208) at ../csu/libc-start.c:308
#4 0x0000555555559f5e in _start ()
```