Description

Out-of-bounds write in function append_command at ex_docmd.c:3447

vim version

git log
commit bfaa24f95343af9c058696644375d04e660f1b00 (HEAD -> master, tag: v8.2.5052, origin/master, origin/HEAD)

POC

./vim -u NONE -i NONE -n -m -X -Z -e -s -S ./poc_obw6_s.dat -c :qa!
=================================================================
==3497672==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x619000000e81 at pc 0x0000004848d9 bp 0x7fffffff5910 sp 0x7fffffff50b0
WRITE of size 3 at 0x619000000e81 thread T0
    #0 0x4848d8 in strcat (/home/fuzz/fuzz-vim/vim/src/vim+0x4848d8)
    #1 0x816a2d in append_command /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:3447:5
    #2 0x7de9e5 in do_one_cmd /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:2619:6
    #3 0x7ca815 in do_cmdline /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:992:17
    #4 0x7c6699 in do_exmode /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:517:6
    #5 0xb5502a in nv_exmode /home/fuzz/fuzz/vim/vim/src/normal.c:3155:2
    #6 0xb2220f in normal_cmd /home/fuzz/fuzz/vim/vim/src/normal.c:941:5
    #7 0x81591e in exec_normal /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:8792:6
    #8 0x815148 in exec_normal_cmd /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:8755:5
    #9 0x814cf9 in ex_normal /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:8673:6
    #10 0x7ddaa9 in do_one_cmd /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:2568:2
    #11 0x7ca815 in do_cmdline /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:992:17
    #12 0xe5aadc in do_source_ext /home/fuzz/fuzz/vim/vim/src/scriptfile.c:1674:5
    #13 0xe57536 in do_source /home/fuzz/fuzz/vim/vim/src/scriptfile.c:1801:12
    #14 0xe56e6c in cmd_source /home/fuzz/fuzz/vim/vim/src/scriptfile.c:1174:14
    #15 0xe5654e in ex_source /home/fuzz/fuzz/vim/vim/src/scriptfile.c:1200:2
    #16 0x7ddaa9 in do_one_cmd /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:2568:2
    #17 0x7ca815 in do_cmdline /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:992:17
    #18 0x7cf4b1 in do_cmdline_cmd /home/fuzz/fuzz/vim/vim/src/ex_docmd.c:586:12
    #19 0x1426b42 in exe_commands /home/fuzz/fuzz/vim/vim/src/main.c:3106:2
    #20 0x1422cdb in vim_main2 /home/fuzz/fuzz/vim/vim/src/main.c:780:2
    #21 0x14183d5 in main /home/fuzz/fuzz/vim/vim/src/main.c:432:12
    #22 0x7ffff7bec082 in __libc_start_main /build/glibc-SzIz7B/glibc-2.31/csu/../csu/libc-start.c:308:16
    #23 0x41ea6d in _start (/home/fuzz/fuzz-vim/vim/src/vim+0x41ea6d)

0x619000000e81 is located 0 bytes to the right of 1025-byte region [0x619000000a80,0x619000000e81)
allocated by thread T0 here:
    #0 0x499ccd in malloc (/home/fuzz/fuzz-vim/vim/src/vim+0x499ccd)
    #1 0x4cb3aa in lalloc /home/fuzz/fuzz/vim/vim/src/alloc.c:246:11
    #2 0x4cb28a in alloc /home/fuzz/fuzz/vim/vim/src/alloc.c:151:12
    #3 0x141843a in common_init /home/fuzz/fuzz/vim/vim/src/main.c:914:19
    #4 0x1417924 in main /home/fuzz/fuzz/vim/vim/src/main.c:185:5
    #5 0x7ffff7bec082 in __libc_start_main /build/glibc-SzIz7B/glibc-2.31/csu/../csu/libc-start.c:308:16

SUMMARY: AddressSanitizer: heap-buffer-overflow (/home/fuzz/fuzz-vim/vim/src/vim+0x4848d8) in strcat
Shadow bytes around the buggy address:
  0x0c327fff8180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c327fff8190: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c327fff81a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c327fff81b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c327fff81c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c327fff81d0:[01]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff81e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c327fff81f0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c327fff8200: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c327fff8210: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c327fff8220: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==3497672==ABORTING

poc_obw6_s.dat

Impact

This may result in corruption of sensitive information, a crash, or code execution among other things.