Heap-based Buffer Overflow in vim/vim

Valid

Reported on

Jan 18th 2022


Description

Heap-buffer-overflow in vim

Proof of Concept

./vim -u NONE -X -Z -e -s -S poc3 -c :qa!

POC3 is here.

Bt

==728741==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x621000025500 at pc 0x0000008961b2 bp 0x7ffca76ad0b0 sp 0x7ffca76ad0a8
READ of size 1 at 0x621000025500 thread T0
    #0 0x8961b1 in utf_head_off /home/zxq/CVE_testing/ASAN-install/vim/src/mbyte.c:3866:9
    #1 0x989caa in block_insert /home/zxq/CVE_testing/ASAN-install/vim/src/ops.c:538:9
    #2 0x9891ee in op_insert /home/zxq/CVE_testing/ASAN-install/vim/src/ops.c:1704:7
    #3 0x99f0ae in do_pending_operator /home/zxq/CVE_testing/ASAN-install/vim/src/ops.c:4179:3
    #4 0x935dfe in normal_cmd /home/zxq/CVE_testing/ASAN-install/vim/src/normal.c:1146:2
    #5 0x71372b in exec_normal /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:8638:6
    #6 0x7132da in exec_normal_cmd /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:8601:5
    #7 0x71300d in ex_normal /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:8519:6
    #8 0x6ed643 in do_one_cmd /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:2573:2
    #9 0x6e043c in do_cmdline /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:993:17
    #10 0xb53dd5 in do_source /home/zxq/CVE_testing/ASAN-install/vim/src/scriptfile.c:1512:5
    #11 0xb513ea in cmd_source /home/zxq/CVE_testing/ASAN-install/vim/src/scriptfile.c:1098:14
    #12 0xb51140 in ex_source /home/zxq/CVE_testing/ASAN-install/vim/src/scriptfile.c:1124:2
    #13 0x6ed643 in do_one_cmd /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:2573:2
    #14 0x6e043c in do_cmdline /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:993:17
    #15 0x6e3a53 in do_cmdline_cmd /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:587:12
    #16 0xf6bf78 in exe_commands /home/zxq/CVE_testing/ASAN-install/vim/src/main.c:3091:2
    #17 0xf690cd in vim_main2 /home/zxq/CVE_testing/ASAN-install/vim/src/main.c:774:2
    #18 0xf61baf in main /home/zxq/CVE_testing/ASAN-install/vim/src/main.c:426:12
    #19 0x7f6f765e20b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
    #20 0x41ee8d in _start (/home/zxq/CVE_testing/ASAN-install/vim/src/vim+0x41ee8d)

0x621000025500 is located 0 bytes to the right of 4096-byte region [0x621000024500,0x621000025500)
allocated by thread T0 here:
    #0 0x4975cd in malloc (/home/zxq/CVE_testing/ASAN-install/vim/src/vim+0x4975cd)
    #1 0x4c70fd in lalloc /home/zxq/CVE_testing/ASAN-install/vim/src/alloc.c:248:11
    #2 0x4c7049 in alloc /home/zxq/CVE_testing/ASAN-install/vim/src/alloc.c:151:12
    #3 0xf72e94 in mf_alloc_bhdr /home/zxq/CVE_testing/ASAN-install/vim/src/memfile.c:884:21
    #4 0xf721fe in mf_new /home/zxq/CVE_testing/ASAN-install/vim/src/memfile.c:376:26
    #5 0x8a77e3 in ml_new_data /home/zxq/CVE_testing/ASAN-install/vim/src/memline.c:4077:15
    #6 0x8c1b04 in ml_append_int /home/zxq/CVE_testing/ASAN-install/vim/src/memline.c:2982:16
    #7 0x8b9e09 in ml_append_flush /home/zxq/CVE_testing/ASAN-install/vim/src/memline.c:3322:12
    #8 0x8b9cc6 in ml_append_flags /home/zxq/CVE_testing/ASAN-install/vim/src/memline.c:3357:12
    #9 0x8b66c7 in ml_append /home/zxq/CVE_testing/ASAN-install/vim/src/memline.c:3344:12
    #10 0x7660d8 in readfile /home/zxq/CVE_testing/ASAN-install/vim/src/fileio.c:2235:8
    #11 0x71ea46 in ex_read /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:7255:10
    #12 0x6ed643 in do_one_cmd /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:2573:2
    #13 0x6e043c in do_cmdline /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:993:17
    #14 0xb53dd5 in do_source /home/zxq/CVE_testing/ASAN-install/vim/src/scriptfile.c:1512:5
    #15 0xb513ea in cmd_source /home/zxq/CVE_testing/ASAN-install/vim/src/scriptfile.c:1098:14
    #16 0xb51140 in ex_source /home/zxq/CVE_testing/ASAN-install/vim/src/scriptfile.c:1124:2
    #17 0x6ed643 in do_one_cmd /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:2573:2
    #18 0x6e043c in do_cmdline /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:993:17
    #19 0x6e3a53 in do_cmdline_cmd /home/zxq/CVE_testing/ASAN-install/vim/src/ex_docmd.c:587:12
    #20 0xf6bf78 in exe_commands /home/zxq/CVE_testing/ASAN-install/vim/src/main.c:3091:2
    #21 0xf690cd in vim_main2 /home/zxq/CVE_testing/ASAN-install/vim/src/main.c:774:2
    #22 0xf61baf in main /home/zxq/CVE_testing/ASAN-install/vim/src/main.c:426:12
    #23 0x7f6f765e20b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/zxq/CVE_testing/ASAN-install/vim/src/mbyte.c:3866:9 in utf_head_off
Shadow bytes around the buggy address:
  0x0c427fffca50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fffca60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fffca70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fffca80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fffca90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c427fffcaa0:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fffcab0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fffcac0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fffcad0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fffcae0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fffcaf0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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
==728741==ABORTING

We are processing your report and will contact the vim team within 24 hours. 4 months ago
zfeixq modified the report
4 months ago
We have contacted a member of the vim team and are waiting to hear back 4 months ago
Bram Moolenaar
4 months ago

Maintainer


The POC is much too long. Please reduce it to the minimal necessary to reproduce the problem.

zfeixq
4 months ago

Researcher


Newpoc is here.

Bram Moolenaar
4 months ago

Maintainer


I can reproduce it now. The POC is still long and a bit obscure, especially because it reads itself. I'll see if I can come up with a simpler test.

Bram Moolenaar validated this vulnerability 4 months ago
zfeixq has been awarded the disclosure bounty
The fix bounty is now up for grabs
zfeixq
4 months ago

Researcher


Thank you.

Bram Moolenaar
4 months ago

Maintainer


Fixed with patch 8.2.4151. The test didn't trigger a valgrind error, could not make it cover the actual problem.

Bram Moolenaar confirmed that a fix has been merged on 57df9e 4 months ago
Bram Moolenaar has been awarded the fix bounty
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