CVE-2022-45492: Heap Overflow in json.h(json_parse_number())

Heap Overflow in json_parse_number()
In json_parse_number(), there is a heap out-of-bound write. The bug can be triggered with an invocation of json_parse_ex() with specific flags combination. The root cause of this vulnerability is that the parameter number transferred to json_parse_number() is not properly sanitized, and it is pointed to out-of-bound position assigned by upper layer function.

Here is the output of Google ASAN when the vulnerability is triggerred:

The flags is 0x5fd6d79cd6247bff

==5128==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6140000001c0 at pc 0x560f532c646f bp 0x7ffc97871f80 sp 0x7ffc97871f78
WRITE of size 8 at 0x6140000001c0 thread T0
#0 0x560f532c646e in json_parse_number /home/hyrathon/Desktop/jsonh/./json.h:1839:18
#1 0x560f532c22d1 in json_parse_value /home/hyrathon/Desktop/jsonh/./json.h:1980:7
#2 0x560f532c08f0 in json_parse_object /home/hyrathon/Desktop/jsonh/./json.h:1719:5
#3 0x560f532c11c8 in json_parse_value /home/hyrathon/Desktop/jsonh/./json.h:1940:5
#4 0x560f532c9c85 in json_parse_ex /home/hyrathon/Desktop/jsonh/./json.h:2129:3
#5 0x560f532e0192 in main /home/hyrathon/Desktop/jsonh/fuzz.c:29:5
#6 0x7f65c9a20d8f in __libc_start_call_main csu/…/sysdeps/nptl/libc_start_call_main.h:58:16
#7 0x7f65c9a20e3f in __libc_start_main csu/…/csu/libc-start.c:392:3
#8 0x560f531ee314 in _start (/home/hyrathon/Desktop/jsonh/san+0x33314) (BuildId: a0e983e1c9c38a8763824dc5481f79d22fe8c82a)

0x6140000001c4 is located 0 bytes to the right of 388-byte region [0x614000000040,0x6140000001c4)
allocated by thread T0 here:
#0 0x560f5327115e in __interceptor_malloc (/home/hyrathon/Desktop/jsonh/san+0xb615e) (BuildId: a0e983e1c9c38a8763824dc5481f79d22fe8c82a)
#1 0x560f532c8f15 in json_parse_ex /home/hyrathon/Desktop/jsonh/./json.h:2088:18
#2 0x560f532e0192 in main /home/hyrathon/Desktop/jsonh/fuzz.c:29:5
#3 0x7f65c9a20d8f in __libc_start_call_main csu/…/sysdeps/nptl/libc_start_call_main.h:58:16

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/hyrathon/Desktop/jsonh/./json.h:1839:18 in json_parse_number
Shadow bytes around the buggy address:
0x0c287fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c287fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c287fff8000: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
0x0c287fff8010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c287fff8020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c287fff8030: 00 00 00 00 00 00 00 00[04]fa fa fa fa fa fa fa
0x0c287fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c287fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c287fff8060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c287fff8070: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c287fff8080: 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
==5128==ABORTING
The input to trigger this bug is attached. The first 8 bytes are the flags for json_parse_ex() and the rest is the content(src). Please use address sanitizer to reproduce the bug, as non-crash overflow is hard to detect or locate without shadow memory.

Version: latest commit (sheredom/json.h@bdcf2e1)

crash-input.zip