PostgreSQL is an advanced object-relational database management system . PL/Perl and PL/Tcl allow users to write PostgreSQL functions in the Perl and Tcl languages. The PostgreSQL SECURITY DEFINER parameter, which can be used when creating a new PostgreSQL function, specifies that the function will be executed with the privileges of the user that created it. It was discovered that a user could utilize the features of the PL/Perl and PL/Tcl languages to modify the behavior of a SECURITY DEFINER function created by a different user. If the PL/Perl or PL/Tcl language was used to implement a SECURITY DEFINER function, an authenticated database user could use a PL/Perl or PL/Tcl script to modify the behavior of that function during subsequent calls in the same session. This would result in the modified or injected code also being executed with the privileges of the user who created the SECURITY DEFINER function, possibly leading to privilege escalation. For Red Hat Enterprise Linux 4, the updated postgresql packages upgrade PostgreSQL to version 7.4.30. If the postgresql service is running, it will be automatically restarted after installing this update.