DBI::SQL::Nano versions from 1.42 before 1.651 for Perl have inverted <= and >= SQL operators on text.

DBI::SQL::Nano, DBI's built-in mini-SQL engine, evaluated WHERE predicates incorrectly in some cases. In the non-numeric string branch of the is_matched method, <= was evaluated using Perl's ge operator, and >= was evaluated using Perl's le operator.

SQL::Nano is the fallback query engine for DBI's file-backed drivers (DBD::File, DBD::DBM, CSV-style drivers) whenever SQL::Statement is not installed, and is forced whenever DBI_SQL_NANO=1. Queries over such tables use these predicates directly.

The impact depends on the context. Where an application relies on a WHERE clause to filter file-backed data for policy or authorization, an inverted <=/>= comparison silently returns the wrong rows.