The xdr_status_vector function in Firebird before 2.1.7 and 2.5.x before 2.5.3 SU1 allows remote attackers to cause a denial of service (NULL pointer dereference, segmentation fault, and crash) via an op_response action with a non-empty status.
https://usn.ubuntu.com/3929-1/
http://www.firebirdsql.org/en/news/security-updates-for-v2-1-and-v2-5-series-66011/
http://www.debian.org/security/2014/dsa-3109
http://lists.opensuse.org/opensuse-security-announce/2014-12/msg00012.html