CVE-2026-116333 PostgreSQL parallel B-tree array scan reads beyond array bounds

This vulnerability is rated as Moderate severity because exploitation requires an authenticated database user with permissions to create custom functions, limiting unauthorized remote access. While an attacker can trigger out-of-bounds memory reads via manipulated parallel query scans, the flaw does not grant write access, data modification, or direct code execution. Earlier major database releases supported across standard enterprise platforms do not implement the vulnerable parallel scan mechanism and are not susceptible to this flaw.

To mitigate this issue without applying code fixes, parallel query execution can be disabled to prevent PostgreSQL from launching parallel workers for index scans:

1. Disable parallel worker processes by setting `max_parallel_workers_per_gather` to `0`. This can be applied across the instance by executing the following SQL command as an administrative user:

ALTER SYSTEM SET max_parallel_workers_per_gather = 0;

SELECT pg_reload_conf();

Alternatively, add or modify the setting in `/var/lib/pgsql/data/postgresql.conf`:

max_parallel_workers_per_gather = 0

Then reload the PostgreSQL service:

systemctl reload postgresql

2. As a supplementary operational control, restrict `CREATE` permissions on schemas and databases to trusted administrators to prevent untrusted users from declaring custom functions.

Caveats:

Disabling parallel query execution forces queries to run in a single process, which can degrade query performance on analytical workloads or large table scans.

Warning: Reloading PostgreSQL configuration files will apply changes to new queries and sessions without dropping active connections, but query execution characteristics will change immediately.