PostgreSQL GB18030 encoding validation can read one byte past end of allocation for text that fails validation

Buffer over-read in PostgreSQL GB18030 encoding validation allows a database input provider to achieve temporary denial of service on platforms where a 1-byte over-read can elicit process termination. This affects the database server and also libpq. Versions before PostgreSQL 17.5, 16.9, 15.13, 14.18, and 13.21 are affected.