CVE-2026-6477

A flaw was found in PostgreSQL libpq. A server superuser can exploit a buffer overflow vulnerability in the PQfn function, which is used by client functions such as lo_export(), lo_read(), lo_lseek64(), and lo_tell64(). This allows the superuser to send an arbitrarily large response, overwriting the client's stack memory, specifically in tools like psql and pg_dump. This could lead to arbitrary code execution on the client system.

This IMPORTANT buffer overflow in PostgreSQL libpq allows a malicious server superuser to overwrite client stack memory via lo_* functions. Exploitation requires the victim to connect to a compromised or malicious server (UI:R). The scope is changed as the server attack affects the client system. Impact is high to confidentiality, integrity, and availability through potential client-side code execution. Affects versions before 18.4, 17.10, 16.14, 15.18, and 14.23.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Only connect to trusted PostgreSQL servers. Avoid using psql or pg_dump against untrusted or potentially compromised database servers.