vim Makefile
DOCKER_GCC=gcc
DOCKER_CLANG=clang
$(DOCKER_GCC) $(CFLAGS) $(TOP_MJS_SOURCES) $(TOP_COMMON_SOURCES) -o $(PROG)
# save the makefile then make
make
$ ./mjs/build/mjs poc.js
=================================================================
===ERROR: AddressSanitizer: heap-buffer-overflow on address 0x604000000138 at pc 0x563a2f179088 bp 0x7fff18d361c0 sp 0x7fff18d361b0
READ of size 8 at 0x604000000138 thread T0
#0 0x563a2f179087 in mjs_disown src/mjs_core.c:288
#1 0x563a2f1c7b54 in mjs_json_parse src/mjs_json.c:480
#2 0x7fff18d3630f (<unknown module>)
Address 0x604000000138 is a wild pointer.
SUMMARY: AddressSanitizer: heap-buffer-overflow src/mjs_core.c:288 in mjs_disown
Shadow bytes around the buggy address:
0x0c087fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c087fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c087fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c087fff8000: fa fa 00 00 00 00 00 00 fa fa 00 00 00 00 00 00
0x0c087fff8010: fa fa 00 00 00 00 00 00 fa fa 00 00 00 00 00 00
=>0x0c087fff8020: fa fa fa fa fa fa fa[fa]fa fa fa fa fa fa fa fa
0x0c087fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c087fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c087fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c087fff8060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c087fff8070: 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
mJS revision
Commit: b1b6eac
Build platform
Ubuntu 18.04.5 LTS (Linux 5.4.0-44-generic x86_64)
Build steps
Test case
poc.js
Execution steps & Output
Credits: Found by OWL337 team.