A PostgreSQL vulnerability identified as CVE-2026-6471, known as PostGREShell, allows attackers with minimal replication access to execute arbitrary code on database servers. This flaw has existed for approximately 12 years and affects non-superuser PostgreSQL accounts with the REPLICATION attribute, commonly used for backup and replication tasks. The vulnerability arises from inadequate restrictions on the library path specified as an output plugin name, enabling an attacker to exploit the logical decoding feature to load a malicious library. Exploitation requires only a PostgreSQL account with REPLICATION privileges, wal_level set to logical, and access to SMB port 445. The flaw was discovered by Cyera Research and dates back to PostgreSQL 9.4's release in 2014. Patches have been released for versions 18.6, 17.11, 16.15, 15.19, and 14.24, and organizations are advised to upgrade to these versions. Database administrators should audit accounts with the REPLICATION attribute and restrict replication connections. Limiting outbound network access and monitoring logical replication activity is also recommended to mitigate risks.