A PostgreSQL security update has been released for Ubuntu Linux 16.04 LTS.

USN-6230-1: PostgreSQL vulnerability

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Ubuntu Security Notice USN-6230-1
July 13, 2023

postgresql-9.5 vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 16.04 LTS (Available with Ubuntu Pro)

Summary:

PostgreSQL could be made to run code with elevated privileges.

Software Description:
- postgresql-9.5: Object-relational SQL database

Details:

Alexander Lakhin discovered that PostgreSQL incorrectly handled certain
CREATE privileges. An authenticated user could possibly use this issue to
execute arbitrary code as the bootstrap supervisor.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 16.04 LTS (Available with Ubuntu Pro):
  postgresql-9.5                     9.5.25-0ubuntu0.16.04.1+esm4
  postgresql-client-9.5           9.5.25-0ubuntu0.16.04.1+esm4

After a standard system update you need to restart PostgreSQL to
make all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-6230-1
  https://ubuntu.com/security/notices/USN-6104-1
  CVE-2023-2454