Firebird is an open-source relational database management system. In versions prior to 5.0.4, 4.0.7 and 3.0.14, the sdl_desc() function does not validate the length of a decoded SDL descriptor from a slice packet. A zero-length descriptor is later used to calculate the number of slice items, causing a division by zero. An unauthenticated attacker can exploit this by sending a crafted slice packet to crash the server. This issue has been fixed in versions 5.0.4, 4.0.7 and 3.0.14.