PostgreSQL superuser privileges pose significant security risks

A technical guide by Umair Shahid explains why granting superuser privileges to applications is dangerous. A superuser can bypass all database permissions, execute shell commands via COPY ... PROGRAM, and read or write files directly on the server. The article provides safer alternatives, such as using dedicated schemas and built-in roles like pg_read_all_data.

Risks and safer alternatives in PostgreSQL

• Superuser capabilities: Can bypass all permission checks, disable row-level security, and use ALTER SYSTEM to change server configuration.
• Host access: Can execute shell commands using COPY ... PROGRAM and run arbitrary code via untrusted languages like plpython3u or plperlu.
• File system access: Can read and write files on the server using pg_read_file and pg_write_file.
• Mitigation via schemas: Assigning a dedicated schema to a role via CREATE SCHEMA ... AUTHORIZATION allows object management without global rights.
• Granular roles: Use pg_read_all_data or pg_write_all_data (introduced in Postgres 14) instead of superuser for broad data access.
• Restricted privileges: Avoid granting CREATEROLE, CREATEDB, or server-file roles like pg_execute_server_program to application accounts.

Why it matters

Encourages better security practices for database administrators and developers to prevent database leaks from escalating into full server compromises.