Andrew Krasichkov discovered that an unprivileged user of dblink or postgres_fdw could bypass the checks intended to prevent use of server-side credentials, such as a ~/.pgpass file owned by the operating-system user running the server. Servers allowing peer authentication on local connections are particularly vulnerable. Other attacks such as SQL injection into a postgres_fdw session are also possible. Attacking postgres_fdw in this way requires the ability to create a foreign server object with selected connection parameters, but any user with access to dblink could exploit the problem. In general, an attacker with the ability to select the connection parameters for a libpq-using application could cause mischief, though other plausible attack scenarios are harder to think of.
For Debian 7 Wheezy, these problems have been fixed in version 9.1.24lts2-0+deb7u3.
We recommend that you upgrade your postgresql-9.1 packages.
Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/