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.
https://www.redhat.com/archives/fedora-package-announce/2009-August/msg01370.html
https://www.redhat.com/archives/fedora-package-announce/2009-August/msg01341.html
https://bugzilla.redhat.com/show_bug.cgi?id=514463