Use After Free in python3.11 (commit  2ab27c4af4ddf752)
Steps to reproduce:

1) ./configure --with-address-sanitizer
2) make
3) ./python <input>

I attach some of the input  that lead to the undefined behavior

For the complete description you can find the asan report here:

==1082579==ERROR: AddressSanitizer: heap-use-after-free on address 0x626000045a40 at pc 0x000000735155 bp 0x7fffffffbed0 sp 0x7fffffffbec8
READ of size 8 at 0x626000045a40 thread T0
    #0 0x735154 in ascii_decode /home/elmanto/ddg/other_targets/cpython/Objects/unicodeobject.c:5091:28
    #1 0x735154 in unicode_decode_utf8 /home/elmanto/ddg/other_targets/cpython/Objects/unicodeobject.c:5158:10
    #2 0xc98381 in syntaxerror /home/elmanto/ddg/other_targets/cpython/Parser/tokenizer.c:1087:15
    #3 0xc8d616 in tok_get /home/elmanto/ddg/other_targets/cpython/Parser/tokenizer.c
    #4 0xc8696b in PyTokenizer_Get /home/elmanto/ddg/other_targets/cpython/Parser/tokenizer.c:1884:18
    #5 0xead74c in _PyPegen_check_tokenizer_errors /home/elmanto/ddg/other_targets/cpython/Parser/pegen.c:1260:17
    #6 0xead74c in _PyPegen_run_parser /home/elmanto/ddg/other_targets/cpython/Parser/pegen.c:1292:17
    #7 0xeaebca in _PyPegen_run_parser_from_file_pointer /home/elmanto/ddg/other_targets/cpython/Parser/pegen.c:1377:14
    #8 0xc83a91 in _PyParser_ASTFromFile /home/elmanto/ddg/other_targets/cpython/Parser/peg_api.c:26:12
    #9 0xa0abf1 in pyrun_file /home/elmanto/ddg/other_targets/cpython/Python/pythonrun.c:1197:11
    #10 0xa0abf1 in _PyRun_SimpleFileObject /home/elmanto/ddg/other_targets/cpython/Python/pythonrun.c:455:13
    #11 0xa09b19 in _PyRun_AnyFileObject /home/elmanto/ddg/other_targets/cpython/Python/pythonrun.c:89:15
    #12 0x4dfe94 in pymain_run_file_obj /home/elmanto/ddg/other_targets/cpython/Modules/main.c:353:15
    #13 0x4dfe94 in pymain_run_file /home/elmanto/ddg/other_targets/cpython/Modules/main.c:372:15
    #14 0x4dfe94 in pymain_run_python /home/elmanto/ddg/other_targets/cpython/Modules/main.c:587:21
    #15 0x4dfe94 in Py_RunMain /home/elmanto/ddg/other_targets/cpython/Modules/main.c:666:5
    #16 0x4e154c in pymain_main /home/elmanto/ddg/other_targets/cpython/Modules/main.c:696:12
    #17 0x4e1874 in Py_BytesMain /home/elmanto/ddg/other_targets/cpython/Modules/main.c:720:12
    #18 0x7ffff7a2e0b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
    #19 0x43501d in _start (/home/elmanto/ddg/other_targets/cpython/python+0x43501d)

0x626000045a40 is located 2368 bytes inside of 10560-byte region [0x626000045100,0x626000047a40)
freed by thread T0 here:
    #0 0x4ada79 in realloc (/home/elmanto/ddg/other_targets/cpython/python+0x4ada79)
    #1 0x638e61 in PyMem_RawRealloc /home/elmanto/ddg/other_targets/cpython/Objects/obmalloc.c:602:12
    #2 0x638e61 in _PyObject_Realloc /home/elmanto/ddg/other_targets/cpython/Objects/obmalloc.c:2339:12

previously allocated by thread T0 here:
    #0 0x4ada79 in realloc (/home/elmanto/ddg/other_targets/cpython/python+0x4ada79)
    #1 0x638e61 in PyMem_RawRealloc /home/elmanto/ddg/other_targets/cpython/Objects/obmalloc.c:602:12
    #2 0x638e61 in _PyObject_Realloc /home/elmanto/ddg/other_targets/cpython/Objects/obmalloc.c:2339:12

SUMMARY: AddressSanitizer: heap-use-after-free /home/elmanto/ddg/other_targets/cpython/Objects/unicodeobject.c:5091:28 in ascii_decode
Shadow bytes around the buggy address:
  0x0c4c80000af0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c4c80000b00: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c4c80000b10: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c4c80000b20: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c4c80000b30: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
=>0x0c4c80000b40: fd fd fd fd fd fd fd fd[fd]fd fd fd fd fd fd fd
  0x0c4c80000b50: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c4c80000b60: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c4c80000b70: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c4c80000b80: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c4c80000b90: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
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
==1082579==ABORTING