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Cemonatk35738A4F-55CE-446C-B836-2FB0B39625F8

HistoryOct 24, 2021 - 11:10 p.m.

Heap-based Buffer Overflow in vim/vim

2021-10-2423:10:51

cemonatk

www.huntr.dev

7.8 High

CVSS3

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

4.6 Medium

CVSS2

Access Vector

LOCAL

Access Complexity

LOW

Authentication

NONE

Confidentiality Impact

PARTIAL

Integrity Impact

PARTIAL

Availability Impact

PARTIAL

AV:L/AC:L/Au:N/C:P/I:P/A:P

0.001 Low

EPSS

Percentile

20.3%

JSON

Description

Greetings,

A Heap-based Buffer Overflow issue was discovered in Vim.

The POC file is reduced to the absolute minimum to reproduce the problem.
Please see sanitizer output and the “trimmed” POC file link below.

System info
OS version : Ubuntu 20.04.2 LTS + Clang 12 with ASan
Vim Version : master(3c5904d) - Sun Oct 24 14:50:07 2021 +0100

Steps to reproduce:

git clone https://github.com/vim/vim

LD=lld-12 AS=llvm-as-12 AR=llvm-ar-12 RANLIB=llvm-ranlib-12 CC=clang-12 CXX=clang++-12 CFLAGS="-fsanitize=address" CXXFLAGS="-fsanitize=address" LDFLAGS="-ldl -fsanitize=address" ./configure --with-features=huge --enable-gui=none && make

Download POC from This URL

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

Sanitizer output:


=================================================================
==136461==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x621000012900 at pc 0x0000004317b6 bp 0x7ffe70040170 sp 0x7ffe7003f930
READ of size 5 at 0x621000012900 thread T0
    #0 0x4317b5 in strlen (/src/fuzzer20/triage_yeni/vim/src/vim+0x4317b5)
    #1 0xe0237e in dec /src/fuzzer20/triage_yeni/vim/src/misc2.c:425:21
    #2 0x16ae424 in bck_word /src/fuzzer20/triage_yeni/vim/src/textobject.c:446:6
    #3 0xec6f2f in nv_bck_word /src/fuzzer20/triage_yeni/vim/src/normal.c:6678:9
    #4 0xe845de in normal_cmd /src/fuzzer20/triage_yeni/vim/src/normal.c:1099:5
    #5 0x9aefb4 in exec_normal /src/fuzzer20/triage_yeni/vim/src/ex_docmd.c
    #6 0x9ad0aa in exec_normal_cmd /src/fuzzer20/triage_yeni/vim/src/ex_docmd.c:8548:5
    #7 0x9ad0aa in ex_normal /src/fuzzer20/triage_yeni/vim/src/ex_docmd.c:8466:6
    #8 0x94ff7b in do_one_cmd /src/fuzzer20/triage_yeni/vim/src/ex_docmd.c:2614:2
    #9 0x94ff7b in do_cmdline /src/fuzzer20/triage_yeni/vim/src/ex_docmd.c:1000:17
    #10 0x136cde4 in do_source /src/fuzzer20/triage_yeni/vim/src/scriptfile.c:1406:5
    #11 0x13699e1 in cmd_source /src/fuzzer20/triage_yeni/vim/src/scriptfile.c:971:14
    #12 0x13699e1 in ex_source /src/fuzzer20/triage_yeni/vim/src/scriptfile.c:997:2
    #13 0x94ff7b in do_one_cmd /src/fuzzer20/triage_yeni/vim/src/ex_docmd.c:2614:2
    #14 0x94ff7b in do_cmdline /src/fuzzer20/triage_yeni/vim/src/ex_docmd.c:1000:17
    #15 0x1bcecfc in exe_commands /src/fuzzer20/triage_yeni/vim/src/main.c:3081:2
    #16 0x1bcecfc in vim_main2 /src/fuzzer20/triage_yeni/vim/src/main.c:773:2
    #17 0x1bc5a8f in main /src/fuzzer20/triage_yeni/vim/src/main.c:425:12
    #18 0x7f54b42f80b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #19 0x41f64d in _start (/src/fuzzer20/triage_yeni/vim/src/vim+0x41f64d)

0x621000012900 is located 0 bytes to the right of 4096-byte region [0x621000011900,0x621000012900)
allocated by thread T0 here:
    #0 0x49a8ad in malloc (/src/fuzzer20/triage_yeni/vim/src/vim+0x49a8ad)
    #1 0x4cc2cb in lalloc /src/fuzzer20/triage_yeni/vim/src/alloc.c:244:11

SUMMARY: AddressSanitizer: heap-buffer-overflow (/src/fuzzer20/triage_yeni/vim/src/vim+0x4317b5) in strlen
Shadow bytes around the buggy address:
  0x0c427fffa4d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fffa4e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fffa4f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fffa500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fffa510: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=&gt;0x0c427fffa520:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fffa530: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fffa540: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fffa550: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fffa560: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fffa570: 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
==136461==ABORTING

References:

CWE-122: Heap-based Buffer Overflow - https://cwe.mitre.org/data/definitions/122.html

This vulnerability is capable of crashing software, bypass protection mechanism, modify of memory, and successful exploitation may lead to code execution