src/remote/server.cpp in fbserver.exe in Firebird SQL 1.5 before 1.5.6, 2.0 before 2.0.6, 2.1 before 2.1.3, and 2.5 before 2.5 Beta 2 allows remote attackers to cause a denial of service (daemon crash) via a malformed op_connect_request message that triggers an infinite loop or NULL pointer dereference.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.