Out-of-bounds write in function append_command in vim/vim

Valid

Reported on

Jun 3rd 2022


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.

We are processing your report and will contact the vim team within 24 hours. 22 days ago
We have contacted a member of the vim team and are waiting to hear back 21 days ago
Bram Moolenaar
19 days ago

Maintainer


I can reproduce it. I can use the POC for a regression test.

Bram Moolenaar validated this vulnerability 19 days ago
TDHX ICS Security has been awarded the disclosure bounty
The fix bounty is now up for grabs
The researcher's credibility has increased: +7
Bram Moolenaar confirmed that a fix has been merged on 44a3f3 19 days ago
Bram Moolenaar has been awarded the fix bounty
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