Common Vulnerabilities and Exposures assigned an identifier CVE-2007-3279 to the following vulnerability: PostgreSQL 8.1 and probably later versions, when the PL/pgSQL (plpgsql) language has been created, grants certain plpgsql privileges to the PUBLIC domain, which allows remote attackers to create and execute functions, as demonstrated by functions that perform local brute-force password guessing attacks, which may evade intrusion detection. References: http://www.securityfocus.com/archive/1/archive/1/471541/100/0/threaded http://www.leidecker.info/pgshell/Having_Fun_With_PostgreSQL.txt http://www.portcullis.co.uk/uplds/whitepapers/Having_Fun_With_PostgreSQL.pdf
Red Hat does not consider this do be a security issue. Creating functions is intended feature of the PL/pgSQL language and is definitely not a security problem. Weak password are generally more likely to be guessed with brute force attacks and choosing a strong password according to good practices is considered to be a sufficent protection against this kind of attack.