Security

• bpo-41304: Fixes python3x._pth being ignored on Windows, caused by the fix for bpo-29778 (CVE-2020-15801).
• bpo-29778: Ensure python3.dll is loaded from correct locations when Python is embedded (CVE-2020-15523).
• bpo-41004: CVE-2020-14422: The hash() methods of ipaddress.IPv4Interface and ipaddress.IPv6Interface incorrectly generated constant hash values of 32 and 128 respectively. This resulted in always causing hash collisions. The fix uses hash() to generate hash values for the tuple of (address, mask length, network address).
• bpo-39603: Prevent http header injection by rejecting control characters in http.client.putrequest(…). Core and Builtins
• bpo-33786: Fix asynchronous generators to handle GeneratorExit in athrow() correctly Library
• bpo-41288: Unpickling invalid NEWOBJ_EX opcode with the C implementation raises now UnpicklingError instead of crashing.
• bpo-39017: Avoid infinite loop when reading specially crafted TAR files using the tarfile module (CVE-2019-20907).
• bpo-41235: Fix the error handling in ssl.SSLContext.load_dh_params(). macOS
• bpo-41100: Additional fixes for testing on macOS 11 Big Sur Intel. Note: macOS 11 is not yet released, this release of Python is not fully supported on 11.0, and not all tests pass.