CVE-2026-111879: DBI versions before 1.656 for Perl hang on a later open of a DBD::DBM table because a failed open_data does not release the table's lock

DBI versions before 1.656 for Perl hang on a later open of a DBD::DBM table because a failed opendata does not release the table's lock.

opendata creates the table's lock file and takes an exclusive flock on it for a CREATE, before the checks that can croak: a dbmmldbm value that is not a module name, a failing tie, or a missing data file. The croak unwinds before the table object is blessed, so nothing releases the lock, and the meta data holding the open descriptor stays cached on the database handle.

The dbmmldbm and dbmtype values come from the DSN or the connect attributes, so a caller that chooses the serializer or the storage backend can trigger the failure.

The flock has no timeout, so a later open of that table (even through a separate database handle) blocks for as long as the handle holding the stale lock lives, in the same process or any other.