This indicates an attack attempt against a Denial of Service vulnerability in PostgreSQL.
The vulnerability is caused by an error when the vulnerable software handles malicious client requests. It allows a remote attacker to crash vulnerable systems via a crafted client request.
PostgreSQL 9.2.x before 9.2.4, 9.1.x before 9.1.9, and 9.0.x before 9.0.13
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor.