The MITRE CVE dictionary describes this issue as:
PostgreSQL 9.2.x before 9.2.4, 9.1.x before 9.1.9, 9.0.x before 9.0.13, and 8.4.x before 8.4.17, when using OpenSSL, generates insufficiently random numbers, which might allow remote authenticated users to have an unspecified impact via vectors related to the "contrib/pgcrypto functions."
Find out more about CVE-2013-1900 from the
MITRE CVE dictionary dictionary and
This issue affects the version of postgresql as shipped with Red Hat Enterprise Linux 5 and 6. This issue affects the version of postgresql84, as shipped with Red Hat Enterprise Linux 5. Red Hat Security Response Team has rated this issue as having low security impact. A future update might address this flaw.