CVE-2026-6471 Allows Replication Accounts to Load Arbitrary Libraries in PostgreSQL 9.4-18

Cyera traced the flaw to the replication protocol parser accepting unsanitized plugin names containing path separators and traversal sequences. The init function of the loaded library executes under the postgres OS account, bypassing the admin-controlled directory restriction that was intended to limit non-superusers. Exploitation requires only a replication slot and an output plugin name; no further authentication is needed once the credential exists.

The same pattern appears in earlier logical replication bypasses and in the 2018 pg_dump directory traversal issues, showing that input handling around plugin and extension loading has remained under-scrutinized for more than a decade. Procurement records indicate logical replication is now default for managed services and backup pipelines, expanding the attack surface beyond self-managed clusters.

Patches released in 18.6, 17.11, 16.15, 15.19, and 14.24 close the path. Operators must also revoke Replication from service accounts that do not perform actual replication, a step rarely audited because the privilege is granted automatically to monitoring and ETL tools.

Unpatched instances will continue to face persistent backdoor risk; the loader trusts any .so placed in a location readable by the postgres user, enabling both immediate RCE and re-entry mechanisms that survive privilege resets.