Vulnerability in core server (CVE-2023-39418)

MERGE fails to enforce UPDATE or SELECT row security policies

PostgreSQL 15 introduced the MERGE command, which fails to test new rows against row security policies defined for UPDATE and SELECT. If UPDATE and SELECT policies forbid some row that INSERT policies do not forbid, a user could store such rows. Subsequent consequences are application-dependent. This affects only databases that have used CREATE POLICY to define a row security policy.

The PostgreSQL project thanks Dean Rasheed for reporting this problem.