typed_ast 1.3.0 and 1.3.1 has an ast_for_arguments out-of-bounds read. An attacker with the ability to cause a Python interpreter to parse Python source (but not necessarily execute it) may be able to crash the interpreter process. This could be a concern, for example, in a web-based service that parses (but does not execute) Python code. (This issue also affected certain Python 3.8.0-alpha prereleases.)
https://github.com/python/typed_ast/commit/dc317ac9cff859aa84eeabe03fb5004982545b3b
https://github.com/python/typed_ast/commit/156afcb26c198e162504a57caddfe0acd9ed7dce
https://github.com/python/cpython/commit/dcfcd146f8e6fc5c2fc16a4c192a0c5f5ca8c53c
https://github.com/python/cpython/commit/a4d78362397fc3bced6ea80fbc7b5f4827aec55e